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physics exam
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Gravity
Terms in this set (53)
Acceleration is defined as the CHANGE in
velocity divided by the time interval
Speed is:
a measure of how fast something is moving, always measured in terms of a unit of distance divided by a unit of time and the distance covered per unit time
Equilibrium occurs when
all the forces acting on an object are balanced, the sum of the +x forces on an object equals the sum of the -x forces, the net force on the object is zero, and the sum of the upward forces equals the sum of the downward forces
in the absence of air resistance, objects fall at constant
speed
If you drop a feather and a coin at the same time in a tube filled with air, which will reach the bottom of the tube first?
the coin
A ball tossed vertically upward rises, reaches its highest point, and then falls back to its starting point, during this time the acceleration of the ball is always
directed upward
The law of inertia states that an object
will continue moving at the same velocity unless an outside force acts on it
will continue moving in a straight line unless an outside force acts on it
that is not moving will never move unless a force acts on it
at rest will remain at rest unless acted on by an outside force
Friction is a force that always acts
opposite to an object's motion
One object has twice as much mass as another object. The first object also has twice as much
inertia
Accelerations are produced by
net forces
If the force acting on a cart doubles, what happens to the cart's acceleration?
it doubles
because of their gravitational attraction, two asteroids are drifting towards each other. as the asteroids get closer together, the force between them
increases
what would happen if, for some reason, the moon slowed down as it orbited the earth, the moon would
not stay in a circular orbit and it could eventually crash in to the earth
electric field lines
Point toward a negative charge, point away from a positive charge, and never cross one another
A table tennis ball launcher is fired, compared to the force on the ball, the force on the launcher is
the same
the momentum of an object is defined as the objects
mass times its velocity
Compared to a sports car moving at 30 miles per hour, the same sports car moving at 60 miles per hour has
twice as much momentum
in order to increase the final momentum of a golf ball we could
increase the force acting on it, follow through when hitting the ball, increase the time of contact with the ball, swing as hard as possible
a girl pulls on a 6-kg wagon with a constant force of 18 N, what is the wagons acceleration
3 m/s
the terminal speed for a person parachuting ( with the chute open) is about
15 km/h
When an object reaches terminal velocity its acceleration is
0 m/s
You pull a 10 kg wagon with a force of 100 N, there is 30 N friction, how much will the wagon accelerate
7 m/s
The reason padded dashboards are used in cars is that they
increase he time of impact in a collision
while roller-skating, granny collides with her tiny grandson Ambrose who is at rest. Ignoring any friction effects, Ambrose's speed after the collision will be greatest when
he and granny make a bouncing collision, each going in opposite directions
a collision is considered elastic if
there is no lasting deformation, the objects don't stick together, the objects that collide don't get warmer, after the collision, the objects have the same shape as before the collision.
a moving freight car runs into an identical car at rest on the track. the cars couple together, compared to the velocity of the first car before the collision, the velocity of the combined cars after the collision is
one half as large
A 15-N force and a 35 -N force act on an object in opposite directions. What is the net force of the object?
20 N
A girl whose weight is 600 N hangs from the middle of a bar supported by two vertical strands of rope. What is the tension in each stand?
300 N
A 6-N falling object encounters 6 N of air resistance. A magnitude of the net force on the object is?
0 N
Suppose you take a trip that covers 180 km and takes 3 hours to make. Your average speed is
40 Km/h
A sheet of paper can be withdrawn from under a container of milk without toppling it if the paper is jerked quickly. The reason this can be done is that
none of above
The Mass of a lamb that weights 110 N is about
11 Kg
How much does a 4.0-kg bag of bolts weigh?
39.2
A large truck and a small car traveling at the same speed have a head -on collision. The vehicle to undergo the greater change in velocity will be
A small car
A 2-kg ball is thrown at 9 m/s. What is the ball's momentum?
18 kg m/s
A piece of putty moving with 3 units of momentum strikes and sticks to heavy bowling ball that is initially at rest. After the putty sticks to the ball , both are set in motion with a combined momentum that is?
3 units
Two gliders having the same mass and speed move toward each other on an air track and stick together. After the collision, the velocity of the gliders is
zero
Suppose the gravitational force between two massive spheres is 40 N. If the distance between the spheres is doubled, What is the force between the masses?
10 N
Suppose the gravitational force between two spheres is 40 N. If the distance stays the same and one mass is tripled , what is the force between the masses?
120 N
A person is attracted towards the center of the Earth by 480-N gravitational force. The force with which Earth is attracted towards the person is?
480 M
Gravity is a force that
attracts
What is the minimum orbital height (above ground) for an earth satellite
150 km
The orbital speed for a satellite orbiting close to Earth is?
8 Km/s
A satellite is always moving _________ to the direction of the force of gravity
perpendicularly
If the moon was closer to the earth, it would have _______ orbital speed to keep it from crashing
Stronger
If the moon was closer to the Earth, it would have to have ______orbital speed to keep it from crashing
Stronger
Three rods of different materials P, Q, and R, are charged by various methods. When the rods are brought near each other, the rods P and Q repel each other, while the rods P and R attract each other.
Which of the following could be the signs of the charges on the rods?
(-) (-) (+)
When two bodies are charged, the total charge before and after charging remains the same because of:
Conservation of charges
A difference between electrical forces and gravitational forces is that electrical forces include
repulsive interactions
A proton has both______and______so it is effected by both gravity and electric fields
mass, charge
If I move two charge plates (middle box above) closer together, what will happen between the plates?
The force will increase
In a motor, a loop of wire is forced to rotate by
A magnetic field forcing the moving electrons (current)
A wire carrying a current is bent into a loop. A magnetic field is strongest
at the center of the loop
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