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Physics Final (Repeats)
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Gravity
Key Concepts:
Terms in this set (207)
What two variables determine the mechanical advantage of a simple machine
Force, distance
A screwdriver can be used to open a can of paint. In this situation, the screwdriver is being used as a
Lever
An oar is used to row a boat. The distance between the oar lock and the rowers hand is 104 cm. This distance is considered
The effort distance
The distance between the rowers hand and fulcrum is 104 cm. The distance between the fulcrum and water is 45 cm. What is the mechanical advantage of the oar
2.31
The mechanical advantage of another oar is 3.00. If the resistance force of the water is 35 N, what is the effort force exerted by the rower?
11.7N
an automotive engineer realizes it will be difficult for drivers to turn a pickup truck with a steering wheel that has a radius of only 11 cm. what can the engineer to increase the mechanical advantage of the steering wheel?
Increase the radius of the steering wheel
If a simple machine in a frictionless environment requires more effort force than a resistance force, then the mechanical advantage value would be:
Less than one
The mechanical advantage for a pulley system is determined by
counting the number of strands holding the resistance force
a 900 N weight is lifted 14 m. using a system of one fixed and two moveable pulleys, find the effort force and the effort distance for the weight
227 N; 55 m
A wheelchair ramp is 10 m long and 1.05 m tall. find the force required to push a wheelchair and a person (combined weight 855 N) up the ramp
92 N
Find the mechanical advange of a jack screw having a pitch of 34 mm and a handle radius of 52 cm
96
The mechanical advantage of a compound machine is determined by
multiplying the mechanical advantage for each simple machine
a pulley system and an inclined plane are being used to slide a crate up a ramp and into a moving truck. the inclined plane is 6 m long and is 1.5 m high. the pulley system uses 4 supporting strands to force the crate up the incline. what is the mechanical advantage of this combined machine?
16
In a second class lever, the distance from the effort to the fulcrum is _______ the distance from the load/resistance to the fulcrum
greater than
if the pulley system shown below (5 strands) is lifting a 50 kg load, what is the minimum amount of effort that must be applied to the system
10 kg
If friction is included in a simple machine, the amount of effort required to move a load will be ______ what is calculated using the formulas for simple machines.
greater than
a TV repairman has to make a delivery of an old and very heavy television. instead of lifting it up 1.0 meter into his truck, the repairman makes a ramp out of a board 4 meters long. he puts the TV on a wheeled platform and pushes it up the board and into the back of his truck. What is the mechanical advantage of the ramp?
4
Find the mechanical advantage of a wheel and axle system if the wheel has a radius of 45 cm and the axle has a radius of 15 cm if the force is put on the axle
.33
the fixed point of rotation on a lever is a
fulcrum
what is the weight (resistance) you could lift using a first-class lever if you apply 20 N of effort? the effort arm is 10 meters and the resistance arm is 5 meters
40 N
determine the ideal mechanical advantage of the pulley system shown in the diagram below (7 strands)
7
scissors are an example of which kind of lever
first
which of the following block and tackle systems has the largest mechanical advantage? A: 5N effort, 10 N load, 2 strands. B: 5N effort, 15N load, 3 strands. C: 5N effort, 20N load, 4 strands
System C has the largest mechanical advantage
A block and tackle machine is used to lift a box that weighs 90 Newtons. How much force do you need to pull on the rope if the machine has a mechanical advantage of 5?
18 N
an electric food processor uses 250 joules of electrical energy every second. due to friction and other causes, the energy available to spin the blades to cut food is reduced to 200 joules per second. the efficiency of the food processor is:
80%
Moment of inertia is the rotational analogue of
mass
a large horizontal disk with a moment of inertia 4000 kg m^2 is rotating on a vertical axis through its center. the disk is coasting at a rate of .150 rev/s when a 90 kg person jumps on to the disk from an overhanging tree limb. The person lands and remains at a distance of 3 m from the axis of rotation. what will be the rate of rotation of the system after the person has landed
.125 rev/s
a certain coin and a wedding ring have exactly the same mass and radius. when placed at the top of the incline, which object reaches the bottom of the incline first?
the coin
The rigid body shown in the diagram below consists of a vertical support post and two horizontal crossbars with spheres attached. the masses of the spheres and the lengths of the crossbars are indicated in the diagram. the body rotates about a vertical axis along the support post with constant angular speed w. if the masses of the support post and the crossbars are negligible, what is the ratio of the angular momentum of the two upper spheres to that of the two lower spheres?
1/8
a light rigid rod with masses attached to its ends is pivoted about a horizontal axis as shown below. when released from rest in a horizontal orientation, the rod begins to rotate with an angular acceleration of magnitude:
g/7L
a rotating merry go round makes one complete revolution in 4 seconds, what is the linear speed of a child seated 1.2 meter from the center
1.9 m/s
the quantity "angular momentum" (in terms of the fundamental quantities of mass, length, and time) is equivalent to:
ML^2T^-1
a small 650 gm ball on the end of a thin, light rod is rotated in a horizontal circle of radius 1.2 m. what is the moment of inertia of the ball about the center of the circle
.936 kgm^2
a neutron star is formed when a n object such as our sun collapses. suppose a uniform spherical star of mass M and radius R collapses to a uniform sphere of radius 10^-5 R. if the original star has a rotational rate of 1 rev each 25 days, what will be the rotational rate of the neutron star
5.0 x 10^3 rev/s
a uniform stick has length L. the moment of inertia about the center f the stick is I. a particle mass M is attached to one end of the stick. the moment of inertia of the combined system about the center of the stick is:
I + 1/4ML^2
a person stands, hands at his side, on a platform that is rotating at a rate of 1.3 rev/s. if he raises his arms to a horizontal position as shown below, the speed of rotation decreases to .8 rev/s. by what factor has his moment of inertia changed
1.6
an objects moment of inertia is 2.0 kgm^2. its angular velocity is increasing at the rate of 5 rad/s. what is the net torque of the object?
10 Nm
If a net torque is applied to an object, that object will experience
an angular acceleration
a ventilation fan with moment of inertia .034 kgm^2 has a net torque of .11 Nm applied to it. what angular acceleration does it experience?
3.2 rad/s^2
The earth moves about the sun in an elliptical orbit. as the earth moves closer to the sun, which of the following best describes the earth-sun systems moment of inertia
decreases
a turntable has a moment of inertia of 3.00 x 10^-2 kgm^2 and spins freely on a frictionless bearing at 25 rev/min. a .3 kg ball of putty is dropped vertically onto the turntable and sticks at point .1 m from the center. what is the new rate of rotation of the system?
22.7 rev/min
according to newtons second law, the angular acceleration experienced by an object is directly proportional to
the net applied torque
a record of mass M and radius R is free to rotate around an axis through its center, O. a tangential force F is applied to the record. what must one do to maximize the angular acceleration?
Make F as large as possible and M and R as small as possible.
rank in decreasing order the distances traveled by objects having the following pairs of average velocity and time of motion.
I. vavg= +2.0 m/s, t= 2.0 sec
II. vavg= +3.0 m/s, t= 2.0 sec
III. vavg= -3.0 m/s, t= 3.0 sec
III, II, I
a crumpled piece of paper hits the ground before a flat sheet of paper because
there is more air resistance against the flat paper
a student walks 3 blocks south, 4 blocks west and 3 blocks north. what is the displacement of the student
4 blocks west
which of the following is the equation for average velocity
vavg= delta x/delta t
rank in decreasing order the displacements of objects having the following pairs of average velocity and time of motion
I. vavg= +2.0 m/s, t= 2.0 sec
II. vavg= +3.0 m/s, t= 2.0 sec
III. vavg= -3.0 m/s, t= 3.0 sec
II, I, III
the displacement of an object undergoing free fall from rest is proportional to:
(delta t)^2
acceleration is defined as
the rate of change of velocity
in one dimensional motion where the direction is indicated by a plus or minus sign, the average velocity of an object has which of the following properties?
It can be positive, negative, or zero
on an unknown planet, an astronaut drops an object from rest. he observes that the object falls a distance of 10 meters during a time interval of 2 seconds. what is the magnitude of the acceleration due to gravity on the planet
5 m/s^2
an object in free fall near the earth's surface
moves only downward
for a scooter with negative acceleration, which of the following statements is always true
The initial velocity of the scooter will be greater than its final velocity
how long would it take a car starting from rest and accelerating uniformly in a straight line at 5 m/s^2 to cover a distance of 200 m?
9 seconds
a single force acts on an object. the components of this force along the +x-axis and the -y-axis. the single force that will being the object into equilibrium has components that act along the
-x-axis and +y-axis
what is the minimum resultant possible when adding a 5 N to an 8 N force
3 N
a window washing rig consists of scaffold supported at each end with 2 vertical cables. the cables each have a breaking strength 5000 N. if the scaffold weighs 350 N, how much additional weight can the rig support?
9650 N
the number of forces that act on a bag of sugar suspended by a weighing scale are
two
the equilibrium rule Ef=0 applies to
objects or systems at rest, or objects or systems in uniform motion in a straight line
two children push on a crate across a smooth floor (ignore friction). child A pushes with 350 N of force to the north. child B pushes with 520 N of force to the east. what is the magnitude of the net force acting on the crate?
627 N
when you press a coiled spring downward, the spring presses upward on your hand with
the same amount of force
when you stand on two bathroom scales, one foot on each scale evenly distributed, each scale will read:
half your weight
The newton is the SI unit for what physical quantity
force
which one of the following is a vector quantity?
Temperature
force
area
distance
force
in the steps of scientific method, what is the next step after formulating and objectively testing hypotheses?
interpreting results
the population of a city rises from 100,000 to 226,000 over a ten-year period. find the average rate of change in people per year
12,600 people per year
the most appropriate SI unit for measuring the length of an automobile is the
meter
a student determines the mass of a rock to be 196 g, but the actual mass of the rock is 200g. the students approximate error is
2%
the average mass of a proton is 1.673 x 10^-27 kg. what is this mass in grams?
1.673 x 10^-24g
the teenager ordered two hamburgers. he must be meeting a friend. this is a(n):
inference
a prediction or statement that can be tested is a(n)
hypothesis
the greek letter delta indicates a(n):
difference or change
Two skaters stand facing each other. One skaters mass is 60 kg and the other's mass is 72 kg. If the skaters push away from each other without spinning
Their momentum are equal but opposite.
If a force is exerted on an object, which statement is true
A small force applied over a long time interval can produce a large change in the objects momentum
A person sitting in a chair with wheels stands up..., causing the chair to roll backwards across the floor. The momentum of the chair
Was zero while stationary and increased when the person stood
Two objects with different masses collide and bounce back after an elastic collision. Before the collision, the two objects were moving at velocities equal in magnitude but opposite in direction. After the collision,
The less massive object had gained momentum
How does the momentum of an object change if the objects velocity and mass doubles
The momentum quadruples
Which of the following involves a change in momentum
A spacecraft travels at constant speed while slowly losing mass
Which of the following statements about the conservation of momentum is NOT correct
Momentum is not conserved for a system of objects in a head on collision
In an inelastic collision between two objects with unequal masses
The momentum of one object will increase by the amount that the momentum of the other object decreases
A roller coaster climbs up a hill at 4 m/s and then zips down the hill at 30 m/s. the momentum of the roller coaster
Is greater down the hill than up the hill
A wooden block of mass M is moving at speed V in a straight line. A bullet is shot at the block against its direction of motion. How fast would the bullet of mass m need to travel to stop the block (assuming that the bullet became embedded inside)
MV/(m+M)
A billiard ball collides with a stationary identical billiard ball in an elastic head on collision. After the collision, which of the following is true of the first ball?
It comes to rest
A big truck collides inelastically with a small car. Which of the following statements is true?
They experience the same magnitude of impulse during the collision
Two objects with equal mass hit a wall with the same velocity. They both bounce back with the same velocity. Both objects experience the same momentum change (impulse) but one experiences twice the force as the other. Which of the following statements is true?
The contact time between the object and the wall of one is one-half the contact time of the other
A 90 kg person is sitting in a boat at rest with a mass of 100 kg. In the boat is a stone with a mass of 5 kg. The person throws the stone at 4 m/s horizontally in the north direction. The velocity of the person and the boat after the throwing stone is
.11 m/s south
Which of the following statements properly relates the variables in the equation F(delta t)= delta ρ
A large constant force acting over a long time interval causes a large change in momentum
A .2 kg baseball is pitched with a velocity of 40 m/s and then is batted to the pitches with a velocity of 60m/s. what is the magnitude of the balls change in momentum?
20 kgm/s
What is the unit of impulse
N.s
A big fish swims up and swallows a small fish at rest. Right after lunch, the velocity of the big fish is
Less than before
A 1400 kg car moving westward with a velocity of 15 m/s collides with a utility pole and is brought to rest in .3 seconds. What is the force exerted on the car during the collision
70,000 N east
Two carts having masses 1.5 kg and .7 kg respectively, are initially at rest and are held together by a compressed spring. When released, the 1.5 kg cart moves left with a velocity of 7 m/s. what is the velocity and direction of the .7 kg car?
15 m/s right
Weight is best described as
The downward force exerted on an object due to gravity
The tendency to remain in constant motion unless acted on by an outside, unbalanced force is called
Inertia
Which of the following correctly states Newton's first law of motion
Every object retains its state of rest or its state of uniform straight line motion unless acted upon an unbalanced force
Which of the following statements are true of both weight and msss
Weight is a force, mass is a measure of inertia
Resistance of object to change its state of rest or motion is termed as
Inertia
For an object of mass 4 kg, which one of the following statements is incorrect
Weight of object on earth= 1/6 x weight of object on moon
Difference between mass and weight is
Mass is quantity and weight is force
A bulb weighs 500 N, its mass in grams would be
50,000 g
How does an astronauts mass while orbiting in the space shuttle compare with his mass while standing on the earths surface
The mass is the same in both places
Which object has more inertia and why? A bowling ball at rest or a high speed soccer ball
Bowling ball. Because it is more massive
What is the acceleration of a crate if two movers apply 85 N and 52.5 N force in the same direction, and a frictional force of 45.5 M acts in the opposite direction of motion? The mass of the crate is 175 kg
...
An astronaut weighs 685 N on earth. What would the astronauts weight be on Jupiter where g=25.9 m/s^2
1810 N
The force of gravity on the moon is 1/6 large as on earth. How does gravitational acceleration on the moon compare with the gravitational acceleration on the earth? Gravitational acceleration will be
1/6 as large on the moon
The unit named after Isaac newton (N) is equivalent to which units
Kg x m/s^2
A .25 kg ball attached to a string is rotating in a horizontal circle of radius .5 m. Assume the tension force is directed horizontally. If the ball revolves twice ever second, what is the tension in the string?
20 N
Which force is responsible for holding a car in an unbanked curve
The force of friction
A split highway has a number of lanes for traffic. For traffic going in one direction, the radius for the inside of the curve is half the radius for the outside. Car A travels on the inside while another car of equal mass, Car B, travels at equal speed on the outside of the curve. Which statement about the resultant forces on the resultant forces on the car is correct
The force on B is half the force on A
The coefficient of static friction for the tires of a race car is .95. The car is on a level circular track of 50 m radius on a planet where g= 2.45 m/s^2 compared to earths g=9.8 m/s^2. The maximum safe speed on the track on the planet is ______ times as large as the maximum safe speed on earth
.5
A car travels around a level highway curve (radius .15 km) at a constant speed of 25 m/s. what is the magnitude of the resultant force acting on the driver who weighs .8 KN
.34 KN
The diagram below represents a ball undergoing uniform circular motion as it travels clockwise on a string. At the moment shown in the diagram, what are the correct directions of both the velocity and centripetal acceleration of the ball
Velocity vector up, acceleration vector right
Centripetal force Fc acts on a car going around a curve. If speed of the car were twice as great, the magnitude of the centripetal force necessary to keep the car moving in the same path would be
4Fc
A 1750 kilogram car travels at a constant speed of 15 meters per second around a horizontal, circular track with a radius of 45 meters. The magnitude of the centripetal force acting on the car is
8750 N
A ball of mass m attached to a light string moves at a constant speed v in a vertical circle with a radius R. Which of the following is true about the magnitude of the net force at point A compared to that at point B
The net force at point A is equal to the net force at point B
A boy stands at the edge of a rotating table. Which of the following forces prevents him from sliding off the table
The static friction
An object moves around a circular path at a constant speed and makes five complete revolutions in 20 seconds. What is the period of rotation
4 seconds
An abject moves at a constant acceleration on a circular path of radius r. Which of the following is the objects velocity
Square root of a x r
An object of mass m movies at a constant speed v around a circular path of radius r. The net force applied on the object is F. What happens to the net force if speed is doubled and radius is quadrupled
Stays the same
A car moves around a circular path of a constant radius at a constant speed. Which of the following statements is true.
The acceleration is directed toward the center
An object rotates with a period 10 s. How many revolutions will it make in 25 seconds
2.5
A 30 kg child rides on a circus ferries wheel that takes her around a vertical circular path with a radius of 20 m every 22 seconds. What is the magnitude of the resultant force on the child at the highest point of this trajectory
49 N
A grindstone spinning at the rate of 8.3 rev/s has what approximate angular speed
52 rad/s
2,600 rev/min is equivalent to which of the following
273 rad/s
When an object is moving with uniform circular motion, the objects tangential speed
Is constant
Which of the following happens due to inertia
A ball whirled in a circular motion will move off in a straight line if the string breaks
Two identical cars, one on the moon and one on earth, are rounding banked curves at the same speed with the same radius and the same angle. The acceleration due to gravity on the moon is 1/6 that of earth. How do the centripetal accelerations of each car compare
The centripetal accelerations are the same for both cars
A race car traveling at 100 m/s enters an unbanked turn of 400 m radius. The coefficient of (static) friction between the tires and the track is 1.1. The track has both an inner and outer wall. Which statement is correct
The race car will crash into the outer wall
Centripetal acceleration must involve a change in
An objects velocity
What term describes a change in the speed of an object in circular motion
Tangential acceleration
Which of the following forces is an example of a contact force
Gravitational force
Electric force
Magnetic force
Frictional force
Frictional force
A change in the force of gravity acting on an object will affect the objects
Weight
A free body diagram represents all of the following except
Forces as vectors
Which of the following statements is true about friction
Friction always opposes the motion or attempted motion
Friction acts in the opposite direction of the normal force
Friction exists only when an object is in motion
Static friction is less than kinetic friction
Friction always opposes the motion or attempted motion
Two forces act on an object. The magnitude of the net forces action on the object
Cannot be determined from the given information
If a nonzero net force is acting on an object, then the object is definitely
Being accelerated
Which of the following is the tendency of an object to maintain its state of motion
Inertia
A force of 5 N and a force of 15 N acting on an object can produce the following forces except
5 N
Which of the following statements does not describe force
Force causes objects at rest to remain stationary
Force cause objects to stop
Force causes objects to start moving
Force causes objects to change direction
Force causes objects at rest to remain stationary
Find the weight of a 75 kg person on earth and on the moon (g=1.63 m/s^2)
735 N; 122 N
A wagon with mass of 300 kg is accelerated across a level surface at .5 m/s^2. What net force acts on the wagon
150 N
Which of the following situations describe inertia
A stationary object tends to resist being moved
A moving object tends to resist a change in direction
A moving object tends to resist a change on speed
All of the above
In general Fnet equals
ΣF
What does the slope of an object accelerating uniformly look like on an acceleration vs time graph
Straight and horizontal
What does slope on a position versus time graph represent
Velocity
What does the slope of a velocity versus time graph represent
Acceleration
A 15 N force and a 45 N force act on an object in opposite directions. What is the net force on the object
30 N
An object is at test suspended from 2 cables. Which of the following properly describes the forces involved
The forces acting upward and downward on the object are balanced
Which of the following statements does not describe force
Force causes objects at rest to remain stationary
The length of a force vector represents the
Magnitude of the force
What term is used to describe the vector sum of all forces acting on an object
Net force
A gymnast whose weight is 500 N hangs from the middle of a bar supported by two vertical stands of rope. What is the tension in each strand
250 N
What is another way to say the force due to gravity
Weight
You are helping your aunt move a piano on wheels from one room to another. When you push the piano horizontally, it moves at constant speed. What can you say about the piano
It is in dynamic equilibrium
Which of the following descriptions best describes an object at rest on a table
The support force is equal to the objects weight
The support force is greater than the objects weight
The support force is less than the objects weight
There is not enough information here
The support force is equal to the objects weight
Marci, who weighs 375 N, stands on a scaffold which weighs 420 N. if tension in the right rope is 450 N, what is the tension in the left rope
345 N
an ant on a picnic table travels 30 cm eastward, then 25 cm northward, and finally 15 cm westward. what is the magnitude of the ant's displacement relative to its original position
29 cm
which of the following is a coordinate system for specifying the precise location of objects
frame of reference
an object thats moving with constant speed travels once around a circular path. true statements about this motion include which of the following?
I. displacement is zero.
II. the average speed is zero.
III. the distance is zero.
I only
an object moves at a constant speed of 6m/s. this means that the object
moves 6 meters every second
a change in a physical quantity w having an initial value wi and final value wf is given by which of the following
wf - wi
identify the following quantities as scalar or vector: the mass of an object, the number of leaves on a tree, wind velocity
scalar, scalar, vector
a boat can move at a constant velocity of 8 km/hr in still water. how long will it take for the boat to move 24 km?
3 hr
you buy a car and the odometer says it has 25,000 km. what does your car odometer read?
distance
you're pedaling your fancy bike and see the speedometer reads 10.5 mph. what does the speedometer reveal?
instantaneous speed
what is the speed of an object at rest
0.0 m/s
the difference between a scalar and a vector can best be summarized by which of the following
vectors include direction
a comet is cruising through the solar system at a speed of 50,000 kmph for a time of 4 hours. what is the distance traveled by the comet during this time?
200 x 10^6 m
which of the following units is the SI unit of speed
meter per second
what is the average speed and the total time of a bus trip when it travels 280 km along a straight path with an average speed of 80 km/hr. the bus stops for a 30 minute break, then travels another 140 km with an average speed of 70 km/hr.
70 km/hr; 6 hrs
which of the following situations represent a negative displacement? (assume positive position is measured vertically along the y axis)
a cat jumps from the ground onto a tree limb
a cat jumps from a tree limb to the ground
a cat stands on a tree limb
a cat jumps from a lower tree limb to a higher one
a cat jumps from a tree limb to the ground
which of the following statements are true of the time of flight for a projectile? list all that apply.
A. for a projectile which lands at the same height that it is projected from, the time to rise to the peak is equal to the time to fall from its peak to the original height.
B. for the same upward launch angles, projectiles will stay in the air longer if the initial velocity is increased
C. the time that a projectile is in the air is dependent upon the vertical component of the initial velocity
D. the time that a projectile is in the air is dependent upon the horizontal component of the initial velocity.
A. for a projectile which lands at the same height that it is projected from, the time to rise to the peak is equal to the time to fall from its peak to the original height.
B. for the same upward launch angles, projectiles will stay in the air longer if the initial velocity is increased
C. the time that a projectile is in the air is dependent upon the vertical component of the initial velocity
a ball is rolled off the edge of a horizontal table. the ball has an initial speed vo and lands on the floor some distance from the base of the table. which of the following statements concerning that fall of the ball is false
one of the components of the final velocity will be vo
a bullet is fired horizontally from a height of 78.4 m and hits the ground 2400 m away. with what velocity does the bullet leave the gun?
600 m/s
which of the following statements are true of the horizontal motion of projectiles? list all that apply.
A. the horizontal velocity of a projectile changes by 9.8 m/s each second
B. a projectile with a horizontal component of motion will have a constant horizontal velocity
C. the horizontal velocity of a projectile is 0 m/s at the peak of its trajectory.
D. the horizontal velocity of a projectile is independent of the vertical velocity
B. a projectile with a horizontal component of motion will have a constant horizontal velocity
D. the horizontal velocity of a projectile is independent of the vertical velocity
which of the following statements are true of the vertical motion of projectiles? list all that apply.
A. the vertical component of a projectiles velocity is a constant value of 9.8 m/s
B. the vertical component of a projectiles velocity is constant.
C. the vertical component of a projectile's velocity is changing.
D. the magnitude of the vertical velocity of a projectile changes by 9.8 m/s each second
C. the vertical component of a projectile's velocity is changing.
D. the magnitude of the vertical velocity of a projectile changes by 9.8 m/s each second
for an object to be projectile, it must be in free fall and its initial velocity must
have a horizontal component
assuming no air friction and ay= - g, the horizontal displacement of a projectile depends on the
horizontal component of its initial velocity and its time in flight
a baby drops a ball from her hand resting on the serving tray on her high chair. simultaneously, she knocks another ball from the same tray. which of the following statements is true
both balls strike the ground at the same time
at school playground, a child runs 5.0 m in the x-direction and then 2.0 m in the y-direction. which one of the following expressions represent the magnitude of the child's resultant displacement
Square root of [(5m)^2 + (2m)^2]
which of the following may be classified as projectile motion?
a thrown baseball
a punted football
water droplet cascading down a waterfall
a thrown baseball
a punted football
water droplet cascading down a waterfall
the motion of a projectile in free fall is characterized by
vx = constant and ay = -g
which displacement at 70 degrees has an x-component of 450 m? what is its y-component?
1.3 km, 1.2 km
a marble rolling with speed 20 cm/s, rolls off the edge of a table that is 80 cm high. (a) how long does it take to drop to the floor? (b) how far, horizontally, from the table edge does the marble strike the floor?
(a) .4 sec, (b) 8.1 cm
in which of the following scenarios is no net work done?
a car accelerates down a hill
a car decelerates on a flat road
a car decelerates as it travels up a hill
a car travels at constant speed on a flat road
a car travels at constant speed on a flat road
a child pulls a balloon for 12 m with a force of 1 N at an angle of 60 degrees below horizontal. how much work does the child do on the balloon
6 J
if the sign of work is negative
the displacement is in the direction opposite to the force
a machine does 2500 joules of work in 1 min. what is the power developed by the machine
42 W
one joule is equivalent to
kg x meter^2 / second^2
the SI unit for power is
watts
a more powerful motor can do
the same work in a shorter time interval
an object is thrown straight up. which of the following is true about the sign of work done by the gravitational force while the object moves up and then down
work is negative on the way up, work is positive on the way down
a block of mass m = 50 kg moves on a rough horizontal surface with a coefficient of kinetic friction μ= .5. the traveled distance is 20 m. how much work is done by the friction force?
-5000 J
a car travels with a constant speed of 15 m/s. the cars engine produces a 4000 N pushing force in order to keep the speed constant. how much power is developed by the engine
60,000 W
a block with a mass of m crosses a rough horizontal surface at a constant speed of v. the coefficient of kinetic friction between the block and the surface is μ. how much power must be produced in order to overcome the friction force?
μmgv
a motorbike engine can develop a power of 90,000 W in order to keep a constant velocity of 30 m/s. what is the applied force
3000 N
a hill is 100 m long and makes an angle of 12 degrees with the horizontal. as a 50 kg jogger runs up the hill, how much work does the jogger against gravity
47,929 J
a curtain that has a mass of 150 kg and needs to be lifted in 5 seconds in order for the show to continue on schedule. if the curtain needs raised a distance of 5.5 meters, what size motor does the theater company need to have measured in watts?
1617 W
how long does it take a 19 kW steam engine to do 6.8 x 10^7 J of work?
60 hrs
a horizontal force of 40 newtons pushes a block along a level table at a constant speed of 2 meters per second. how much work is done on the block in 6 seconds?
480 J
Car A and CAr B are of equal mass and travel up a hill. car A moves up the hill at a constant speed that is twice the constant speed of car B. compared to the power developed by car B, the power developed by car A is
half as much
an electric motor lifts a 10 kg mass 100 meters in 10 seconds. the power developed by the motor is
980 W
a 1.0 kg mass falls a distance of .5 meter, causing a 2 kg mass to slide the same distance along a table top. how much work is done by the falling mass?
4.9 J
which symbolic expression shows how the unit of work (joule) is related to the fundamental units of kg, m, and sec
Kg x m^2/s^2
the rate at which a force does work may be measured in
watts
Which of the following statements uses work in the scientific sense?
Stan goes to work in the bus
Anne did work of the project for 5 hrs
joseph found that holding the banner in place was hard work
an engine does work on a car when the car is moving
an engine does work on a car when the car is moving
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