Physics 203A - Final Exam

### True or False? The acceleration is always the slope of the "velocity versus time" graph and the velocity is always the slope of the "position versus time" graph.

True

### True or False? If an object stops moving at a point, then its acceleration must be zero at that point

False

### It is physically impossible for an object to have a negative acceleration and yet be speeding up.

False

###
A ball is thrown vertically upward and then comes back down. During the ball's flight up and down, its velocity and acceleration vectors are

A) always in opposite directions.

B) always in the same direction.

C) first in opposite directions and then in the same direction.

D) first in the same direction and then in opposite directions

first in opposite directions and then in the same direction.

### True or False? A ball is thrown at an angle above the horizontal from the top of a cliff and feels no air resistance. A runner at the base of the cliff moves horizontally so that she is always under the ball. In this runner's reference frame, the path of the ball is a straight line rather than a parabola.

True

###
Two bullets are fired simultaneously parallel to a horizontal plane. The bullets have different masses and different initial velocities. Which one will strike the plane first?

A) the fastest one

B) the slowest one

C) the heaviest one

D) the lightest one

E) They strike the plane at the same time.

They strike the plane at the same time.

###
The figure shows an object's acceleration-versus-force graph. What is the object's mass in grams?

A) 2.5

B) 1.6

C) 630

D) 400,000

2.5

### True or False? If you pound a feather with a hammer, the feather always pushes on the hammer just as hard as the hammer pushes on the feather

True

### True or False? A bucket is being lowered by a rope with a constant downward acceleration. The tension in the rope must be equal to the weight of the bucket

False

### True or False? A 75 pound box rests on a perfectly smooth horizontal surface. Any horizontal force greater than zero will cause it to start moving

True

###
If you were to move into outer space far from any stars or planets,

A) your mass would change, but your weight would not change.

B) your weight would change, but your mass would not change.

C) both your weight and mass would change.

D) neither your weight nor your mass would change

your weight would change, but your mass would not change.

###
A cyclist is riding up a hill having a constant slope of 30º with respect to the horizon at a constant speed (in a straight line). Which statement is true?

A) The net force on the bike (due to gravity, the normal force, and friction) is zero.

B) The net force on the bike (due to gravity, the normal force, and friction) is in the direction of motion.

C) The net force on the bike (due to gravity, etc...)is in the opposite direction of motion.

The net force on the bike (due to gravity, the normal force, and friction) is zero.

### True or False? If you swing a ball in a vertical circle using a thin string, at the bottom of the circle the tension in the string must be greater than the ball's weight

True

### True or False? An ordinary car would not be able to go around an unbanked curve of a perfectly smooth road, no matter how the driver turned the wheels

True

###
If you stood on a planet having a mass four times higher than Earth's mass, and a radius two times longer than Earth's radius, you would weigh

A) the same as you do on Earth.

B) two times more than you do on Earth.

C) two times less than you do on Earth.

D) four times more than you do on Earth

the same as you do on Earth.

### True or False? If a spinning object has a negative angular acceleration, it must be slowing down

False

### True or False? A rubber ball moving horizontally at 8.50 m/s hits a brick wall and bounces back with exactly the same speed but in the opposite direction. During this collision, its change in momentum is zero.

False

### True or False? In a collision between a small car and a large truck, the car and the truck undergo the same change in their velocities

False

### True or False? A long vertical metal cylinder is filled with oil. If a piston pushes on the top of this cylinder and increases the pressure there by 6,000 Pa, the pressure at the bottom will increase considerably more due to the weight of the oil

False

### True or False? According to Pascal's principle, if you increase the pressure enough so that the force at one end of an oil-filled tube increases by 10 N, the force will increase at all points in the tube by 10 N.

False

### True or False? Water flows through a pipe having a varying width. More water flows per second through the wide section than through the narrow section because there is more room for it to flow

False

###
A wooden block contains some nails so that its density is exactly equal to that of water. If it is placed in a tank of water and released from rest when it is completely submerged, it will

A) rise to the surface.

B) sink to the bottom.

C) remain where it is released

remain where it is released

###
The Bernoulli effect is responsible for the lift force on an airplane wing. Wings must therefore be designed so as to insure that:

A) air molecules will be deflected downward when they hit the wing.

B) air molecules will be deflected upward when they hit the wing.

C) air molecules move more rapidly past the upper surface of the wing than past the lower surface.

D) air molecules move more rapidly past the lower surface of the wing than past the upper surface

air molecules move more rapidly past the upper surface of the wing than past the lower surface.

### True or False? If the average speed of an object is zero, then its average velocity must be zero; but if its average velocity is zero, its average speed is not necessarily zero.

True

### True or False? The acceleration is always the slope of the "velocity versus time" graph and the velocity is always the slope of the "position versus time" graph

True

### True or False? If an object stops moving at a point, then, its acceleration must be zero at that point.

False

### True or False? If you throw a rock in a lake at 35° or 60° from horizontal, with the same initial speed, it will splash on the same spot

False

### True or False? It is physically impossible for an object to have a negative acceleration and yet be speeding up.

False

###
While in flight, how do the x and y components of the velocity vector of the ball compare at the points B and C?

A) The velocity components are non-zero at B and zero at C.

B) The x components are the same; the y component at C is zero m/s.

C) The x components are the same; the y component has a larger magnitude at C than at B.

D) The x component is larger at C than at B; the y component at B points up while at C, it points downward.

The x components are the same; the y component at C is zero m/s.

###
Which of the following ideas is true about projectile motion with no air drag?

A) v^2x + v^2y = constant.

B) The acceleration is +g when the object is rising and -g when falling.

C) The total velocity of the object is zero at the point of maximum elevation.

D) The horizontal motion is independent of the vertical motion

The horizontal motion is independent of the vertical motion

###
Two bullets are fired simultaneously parallel to a horizontal plane. The bullets have different masses and different initial velocities. Which one will strike the plane first?

A) the fastest one

B) the slowest one

C) the heaviest one

D) the lightest one

E) They strike the plane at the same time.

They strike the plane at the same time.

###
Which one of the following statements concerning kinetic energy is true?

A) Kinetic energy can be measured in watts.

B) Kinetic energy is always equal to the potential energy.

C) Kinetic energy is always positive.

D) Kinetic energy is a quantitative measure of inertia

Kinetic energy is always positive.

### True or False? In a collision between a huge SUV and a small compact car, the SUV exerts a larger force on the compact than the compact exerts on the SUV.

False

###
A block is at rest on a rough incline as shown The frictional force acting on the block, along the incline, is

A) zero.

B) equal to the weight of the block.

C) greater than the weight of the block.

D) less than the weight of the block.

less than the weight of the block.

###
Which one of the following terms is used to indicate the natural tendency of an object to remain at rest or in motion at a constant speed along a straight line?

A) velocity

B) inertia

C) acceleration

D) equilibrium

E) force

Inertia

###
A rock of weight 2.0-N slides on a frictionless inclined plane. Which one of the following statements is true concerning the normal force that the plane exerts on the rock?

A) The normal force is zero newtons.

B) The normal force is 2.0 N.

C) The normal force is less than 2.0 N, but greater

The normal force is less than 2.0 N, but greater than zero newtons.

###
A rock is suspended from a string; and it accelerates downward. Which one of the following statements concerning the tension in the string is true?

A) The tension points downward.

B) The tension is less than the weight of the rock.

C) The tension is equal to the weight of the rock.

D) The tension is greater than the weight of the rock.

The tension is less than the weight of the rock.

### True or False? It is not physically possible for the "position versus time" graph of a moving animal to be either perfectly vertical or perfectly horizontal

True

### True or False? If an object stops moving at a point, then its acceleration must be zero at that point

False

### True or False? It is physically impossible for an object to have a negative acceleration and yet be speeding up.

False

### True or False? If the "velocity versus time" graph of an object is a horizontal line, that object cannot be accelerating.

True

###
True or False? A tennis ball following a parabolic trajectory without air resistance has two forces acting on it; gravity downward and a force

keeping it moving forward

False

###
True or False? A grasshopper leaps into the air at a 62 degree angle above the horizontal. At its highest point, the grasshopper's velocity and

acceleration are equal to zero.

False

###
True or False? You throw a 5.0 kg stone from the top of a cliff with an initial vertical velocity of 8.0 m/s downward and an initial horizontal

velocity of 7.0 m/s away from the cliff, and it feels no air

resistance. After the stone is in the air but free of your hand, its

acceleration remains constant at 9.8 m/s2 downward but its speed

changes

True

###
A bicyclist is riding at a constant speed along a straight-line

path. The rider throws a ball straight up to a height a few meters

above her head. Ignoring air resistance, where will the ball land?

a. behind the rider

b. in front of the rider

c. in the same hand that threw the ball

d. in the opposite hand to the one that threw it

e. This cannot be determined without knowing

in the same hand that threw the ball

###
A baseball is hit upward and travels along a parabolic arc before it

strikes the ground. Which one of the following statements is

necessarily true?

a. The acceleration of the ball decreases as the ball moves

upward.

b. The velocity of the ball is zero m/s when the ball is at the

highest point in the arc.

c. The acceleration of the ball is zero m/s2 when the ball is at

the highest point in the arc.

d. The x-component of the velocity of the ball is the same

throughout the ball's flight.

e. The velocity of the ball

The x-component of the velocity of the ball is the same

throughout the ball's flight.

###
A spring-loaded gun is aimed horizontally and is used to launch

identical balls with different initial speeds. The gun is at a fixed

position above the floor. The balls are fired one at a time.

If the speed of the second ball fired is twice the speed of the first ball fired, how is the

horizontal range (denoted R in the figure) affected?

a. The range for both balls will be the same.

b. The range of the second ball will be half as much as that of

the first ball.

c. The range of the second ball will be twice as large as that

of the first ball.

d. The range of the second ball is about 1.4 times larger than

that of the first ball.

e. The range of the second ball will be smaller than that of the

first ball by a factor of 1.4.

The range of the second ball will be twice as large as that

of the first ball.

### True or False? In a collision between a huge SUV and a small compact car, the SUV exerts a larger force on the compact than the compact exerts on the SUV.

False

For every action there is a reaction, equal in magnitude and opposite in direction. According to the third law of mechanics the compact car will react with the same force.

### True or False? If you pound a feather with a hammer, the feather always pushes on the hammer just as hard as the hammer pushes on the feather

True

### True or False? A crate is sliding down an inclined ramp at a constant speed of 0.55 m/s. The vector sum of all the forces acting on this crate must point down the ramp.

False

Constant velocity means zero acceleration, therefore no net force despite the fact that the crate is moving. Moving object does not mean there is a net force. That would be Aristotle's thinking!

### True or False? A bucket is being lowered by a rope with a constant downward acceleration. The tension in the rope must be equal to the weight of the bucket

False

### True or False? A stone rolls down a sloping hillside. The normal force that the surface of the hill exerts on the stone is equal to the stone's weight

False

### True or False? A 75 pound box rests on a perfectly smooth horizontal surface. Any horizontal force greater than zero will cause it to start moving

True

### True or False? If the mass of Earth and all objects on it were suddenly doubled, the acceleration due to gravity at the surface would become 4 times what it is now.

False

###
If you stood on a planet having a mass four times higher than Earth's mass, and a radius two times longer than Earth's radius, you would weigh

a. the same as you do on Earth

b. two times more than you do on Earth.

c. two times less than you do on Earth

d. four times more than you do on Earth.

e. four times and as half more than you do on Earth.

f. six times more than you do on Earth.

the same as you do on Earth

###
A donkey pulls a crate up a rough, inclined plane at constant speed.

Which one of the following statements concerning this situation is

FALSE?

a. The gravitational potential energy of the crate is increasing.

b. The net work done by all the forces acting on the crate is

zero joules.

c. The work done on the crate by the normal force of the plane is

zero joules.

d. The donkey does "positive" work in pulling the crate up the

incline.

e. The work done on the object by gravity is zero joules.

The work done on the object by gravity is zero joules.