physics u4 multiple choice review

If electricity costs 7.06¢/kW•h, how much would it cost you to run a 120-W stereo system 4.0 hours per day for 4.0 weeks?

$0.95

A 30-N box is pulled upward 6.0 m along the surface of a ramp that rises at 37° above the horizontal. How much work does gravity do on the box during this process?

-110 J

A 35-N bucket of water is lifted vertically 3.0 m and then returned to its original position. How much work did gravity do on the bucket during this process?

0 J

A force produces power P by doing work W in a time T. What power will be produced by a force that does six times as much work in half as much time?

12P

How many joules of energy are used by a 1.0-hp motor that runs for 1.0 hour? (1 hp = 746 W)

2.7 MJ

How large a net force is required to accelerate a 1600-kg SUV from rest to a speed of 25 m/s in a distance of 200 m?

2500

How much kinetic energy does a 0.30-kg stone have if it is thrown at 44 m/s?

290 J

How much work must be done by frictional forces in slowing a 1000-kg car from 26.1 m/s to rest?

3.41 × 105 J

A tiger is running in a straight line. If we double both the mass and speed of the tiger, the magnitude of its momentum will increase by what factor?

4

A traveler pulls on a suitcase strap at an angle 36° above the horizontal. If 555 J of work are done by the strap while moving the suitcase a horizontal distance of 15 m what is the tension in the strap?

46 N

If 4.0 J of work are performed in stretching an ideal spring with a spring constant (force constant) of 2500 N/m, by what distance is the spring stretched?

5.7 cm

Matthew pulls his little sister Sarah along the horizontal ground in a wagon. He exerts a force on the wagon of 60.0 N at an angle of 37.0° above the horizontal. If he pulls her a distance of 12.0 m, how much work does Matthew do?

575 J

A child does 350 J of work while pulling a box from the ground up to his tree house at a steady speed with a light rope. The tree house is 4.0 m above the ground. What is the mass of the box?

8.9 kg

How much work would a child do while pulling a 12-kg wagon a distance of 4.3 m with a 22 N force?

95 J

A 4.0 kg object is moving with speed 2.0 m/s. A 1.0 kg object is moving with speed 4.0 m/s. Both objects encounter the same constant braking force, and are brought to rest. Which object travels the greater distance before stopping?

Both objects travel the same distance.

You and your friend, who weighs the same as you, want to go to the top of the Eiffel Tower. Your friend takes the elevator straight up. You decide to walk up the spiral stairway, taking longer to do so. Compare the gravitational potential energy of you and your friend, after you both reach the top.

Both of you have the same amount of gravitational potential energy at the top.

A firecracker explodes in midair and breaks up into many fragments. Which of the following statements are true regarding conditions immediately before and immediately after the explosion:

I. The total momentum of the fragments is equal to the original momentum of the firecracker.

A truck has four times the mass of a car and is moving with twice the speed of the car. If K t and K c refer to the kinetic energies of truck and car respectively, it is correct to say that

K t = 16K c.

For an elastic collision, which of the following statements are true?

Kinetic energy is conserved. and Momentum is conserved.

For an INELASTIC collision, which of the following statements are true?

Kinetic energy is gained. , Kinetic energy is lost. and Momentum is conserved.

A very light ping-pong ball moving east at a speed of 4 m/s collides with a very heavy stationary bowling ball. The Ping-Pong ball bounces back to the west, and the bowling ball moves very slowly to the east. Which object experiences the greater magnitude impulse during the collision?

Neither; both experienced the same magnitude impulse.

Person B does twice the work of person A, and in one-half of the time . How does the power output of person B compare to person A?

Person B has four times the power output of person A.

Which one has larger kinetic energy: a 500-kg object moving at 40 m/s or a 1000-kg object moving at 20 m/s?

The 500-kg object

Two cyclists who weigh the same and have identical bicycles ride up the same mountain, both starting at the same time. Joe rides straight up the mountain, and Bob rides up the longer road that has a lower grade. Joe gets to the top before Bob. Ignoring friction and wind resistance, which one of the following statements is true?

The amount of work done by Joe is equal to the amount of work done by Bob, but the average power exerted by Joe is greater than that of Bob.

A 5-kg ball collides inelastically head-on with a 10-kg ball, which is initially stationary. Which of the following statements is true?

The magnitude of the change of velocity the 5-kg ball experiences is greater than that of the 10-kg ball. and The magnitude of the change of the momentum of the 5-kg ball is equal to the magnitude of the change of momentum of the 10-kg ball.

If the net work done on an object is positive, what can you conclude about the object's motion?

The object is speeding up.

If the net work done on an object is zero, what can you determine about the object's kinetic energy?

The object's kinetic energy remains the same.

If the force on an object is in the negative direction, the work it does on the object must be

The work could be either positive or negative, depending on the direction the object moves.

A graph depicts force versus position. What represents the work done by the force over the given displacement?

The work done is equal to the area under the curve.

You throw a baseball straight up. Compare the sign of the work done by gravity while the ball goes up with the sign of the work done by gravity while it goes down.

The work is negative on the way up and positive on the way down.

In an inelastic collision involving an isolated system, the final total momentum is

exactly the same as the initial momentum.

Jill does twice as much work as Jack does and in half the time. Jill's power output is

four times Jack's power output.

A stone is held at a height h above the ground. A second stone with four times the mass of the first one is held at the same height. The gravitational potential energy of the second stone compared to that of the first stone is

four times as much

Which of the following quantities are units of impulse?

kg • m/s and N • s

Is it possible for the kinetic energy of an object to be negative?

no

A pendulum bob swings from point A to point B along the circular arc; Is the work done on the bob by gravity positive, negative, or zero? ; Is the work done on the bob by the string positive, negative, or zero?

positive; zero

A rubber ball and a lump of clay have equal mass. They are thrown with equal speed against a wall. The ball bounces back with nearly the same speed with which it hit. The clay sticks to the wall. Which one of these objects experiences the greater momentum change?

the ball

Two objects of different mass have equal, non-zero kinetic energies. Which object has the greater magnitude momentum?

the heavier object

Two objects of different masses have momentum of equal, non-zero magnitude. Which object has more kinetic energy?

the lighter object