Physics Unit 3

Which car in the data table above has the greatest momentum?

III

A father (100 kg) and his son (50 kg) are jogging at the same speed. Which statement is true about the kinetic energies (K) of the father and the son?

kinetic energy of the father = double the kinetic energy of the son

The diagram above represents two masses before and after they collide. Before the collision, mass mA is moving to the right with speed v, and mass mB is at rest. Upon collision, the two masses stick together. Which expression represents the speed, v', of the masses after the collision? [Assume no outside forces are acting on mA or mB.]

mAv / (mA + mB)

Two cars having different weights are traveling on a level surface at different constant velocities. Within the same time interval, greater force will always be required to stop the car that has the greater

momentum

A large moving ball collides with a small stationary ball. The momentum

of the large ball decreases, and the momentum of the small ball increases

A force is applied to stop a moving shopping cart. Increasing the distance over which the work is done:

requires a smaller force

As a car is slowed, most of its mechanical kinetic energy is converted by the brakes to:

thermal energy

Suppose a girl is standing on a pond where there is no friction between her feet and the ice. In order to get off the ice, she can

throw something in the direction opposite to the way she wants to go

A spring-loaded ballistic cart measuring 190 g is in contact with a second 530 g cart. The carts are initially at rest on a level surface. The spring is released and the lighter cart is observed to move at +0.69 m/s afterward. What is the velocity of the other cart?

-0.25 m/s

During batting practice, a 0.30 kg baseball is hit with a bat that exerts a force of 350 N on the ball. The ball left the bat at 80.0 m/s. If the incoming pitch was traveling at 60.0 m/s, how long did the ball stay in contact with the bat?

0.12 s

An air bag applies a force of 4900 N to bring about a change in momentum of 2060 kgm/s. How much time did it act over?

0.42 s

A ball is hit with a bat. A student determines that the momentum of the ball is 1.0 kilogram meter per second. What is the mass of the ball if it has a velocity of 2.0 meters per second?

0.50 kg

A 3.00 kilogram mass is attached to a spring (k = 30.0 N/m) . The mass is pulled 0.200 meters from the spring's equilibrium position. How much spring potential energy is being stored by the mass-spring system?

0.600 J

5 N of force is being applied to an object for 10 seconds, but the object does not move. How much work is being done?

0J

As shown in the diagram above, a student exerts an average force of 600 Newtons on a rope to lift a 50 kg crate a vertical distance of 3.0 meters. Approximately how much work does the student do?

1,800 J

If car I in the data table above were to collide head-on with car IV and the two cars locked together into a single moving pile, what would their combined momentum be?

1.0 kgm/s west

Approximately how high did a worker lift a bag of sand weighing 400 N if he used 4,000 J of energy? Assume no energy is used to overcome friction.

10 m

How much power is necessary to do 50.0 Joules of work in 5.00 seconds?

10.0 W

A block sliding on a frictionless surface is moving with a velocity of 9.0 m/s. The mass of the block is 8.0 kg. An impulse is applied on the block as shown on the graph. What is the block's speed at time t = 6 s?

11 m/s

Assuming that the rollercoaster car has a mass of 500 kg, then the Gravitational Potential Energy at the top of the first hill is closest to

147,000 J

As shown in the diagram above, a 0.50 meter long spring is stretched from its equilibrium position to a length of 1.00 meter by a weight. If the spring constant for this particular spring is 120 N/m, how much energy has been stored in the spring?

15 J

A pulley is used to lift a box that weighs 90.0 N. How much force do you need to pull on the rope if the pulley has a mechanical advantage of 5.00?

18.0 N

A 1800 kg car with the brakes applied comes to a stop in 5.20 s. During these 5.20 s the force of friction slowing down the car is 3500.0 N. What is the change in momentum of the car?

18200 kgm/s

The weight lifter used a force of 980 N to raise the barbell over his head in 5.21 seconds. Approximately how much work did he do in raising the barbell?

2,000 J

An apple has 10.0 J of gravitational potential energy when hanging from a branch in a tree. When the apple drops, at 1.0 m above the ground it has 8.0 J of mechanical kinetic energy due to the speed at which it is falling. How much gravitational potential energy would it have at this point (neglecting any loss due to air resistance)?

2.0 J

A 75 kg object traveling 15 m/s collides with and sticks to a 315 kg object initially at rest. What is the final velocity of the two objects?

2.88 m/s

A 0.05 kg bullet is fired from a 4.0 kg rifle that is initially at rest. If the bullet leaves the rifle with a momentum having a magnitude of 20 kgm/s, the rifle will recoil with a momentum of having a magnitude of

20 kgm/s

A 1,000 kg cannon fires a 10 kg projectile horizontally at a velocity of 300 m/s. What is the magnitude of the recoil velocity of the cannon?

3 m/s

A dogsled team has a total momentum of 1710 kgm/s. If the team has a total mass of 450 kg, what is its speed?

3.8 m/s

What impulse must be applied to a 25.0 kg cart to cause a velocity change of 12.0 m/s?

300. Ns

If car II in the data table above were to collide head-on with car III and the two cars locked together into a single moving pile, what would their combined momentum be?

4.0 kgm/s east

Calculate the work needed to lift a block weighing 4.00 N a distance of 10.0 meters.

40.0 J

A model rocket with an initial mass of 3.0 kg is launched horizontally by burning and expelling 760 g of fuel with a velocity of 150 m/s. What is the velocity of the rocket after the fuel is expelled? (Assume the propellant is expelled instantaneously.)

51 m/s

A 0.149 kg baseball, initially moving at 15 m/s is brought to rest in 0.04 seconds by a baseball glove on a catcher's hand. The magnitude of the average force exerted on the ball by the glove is

56 N

A crane lifts a load of steel 250.0 meters into the air. The steel has a mass of 2,500.0 kg. How much energy is used by the crane?

6,130,000 J

A crane lifts a load of steel 250.0 meters into the air. The steel has a mass of 2,500.0 kg. How much work did the crane do on the steel?

6,130,000 J

What is the momentum of a cat of mass 4.0 kg that is running south with a speed of 1.5 m/s?

6.0 kgm/s south

A 13 N horizontal force acts in the same direction as a 6.4 kg block as it slides 2.5 m/s on a frictionless, horizontal surface for 2.1 s. What is the speed of the block after force is applied?

6.8 m/s

A 1000.0 kg car sliding on frictionless ice at 22 m/s hits a stationary 2200.0 kg minivan. The two vehicles are locked together after impact on the ice. What is their speed after impact?

6.9 m/s

What is the momentum of a dog of mass 20 kg that is running east with a speed of 3 m/s?

60 kgm/s

If you push on a door for 12 seconds with a force of 53 N, how much impulse have you applied to the door?

636 Ns

A bowling ball has a mass of 4.3 kg and is traveling with a velocity of 16 m/s down the lane. How much momentum does it have?

69 kgm/s

A diver with a mass of 80.0 kg dives off a platform. His velocity just before striking the water is 14.0 m/s. What is his kinetic energy at that moment?

7,840 J

A crane lifts a load of steel 250.0 meters into the air. The steel has a mass of 2,500.0 kg. If the crane performed this feat in 85 seconds, how much power does the crane use?

72,000 W

The difference in momentum between a 53.0 kg athlete running 3.58 m/s and a 880.0 kg car traveling 1.03 m/s is closest to:

720 kgm/s

During the first 10 seconds of a rocket launch, the momentum of the rocket increased by 8000 kgm/s. What was the impulse applied to the rocket during this time?

8,000 Ns

A 1.0 kg model rocket's engine is designed to deliver an impulse of 6.0 Newton-seconds. If the rocket engine burns for 0.75 seconds, what average force does it produce?

8.0 N

An electric food processor uses 250.0 Joules of electrical energy. Due to friction and other causes, the energy available to spin the blades to cut food is reduced to 200.0 Joules. The efficiency of the food processor is:

80.00 %

Car A is moving to the right with a speed of 16 m/s and car B is moving to the left with a speed of 7.5 m/s. Both cars have a mass of 1000.0 kg. What is the total momentum of the system consisting of cars A and B? (You may define positive direction to be to the right)

8500 kgm/s

An airplane has a momentum of 22,125 kgm/s. If the airplane moves at a speed of 25.0 m/s, what is its mass?

885 kg

The momentum of a car is 13,300 kgm/s. If it has a speed of 14 m/s, what is the mass of the car?

950 kg

A wound spring provides the energy to propel a toy car across a level floor. At time ti ,the car is moving at speed viacross the floor and the spring is unwinding, as shown below. At time tf, the spring has fully unwound and the car has coasted to a stop.

Both elastic potential energy and kinetic energy at ti are converted to thermal energy at tf

You burn a log on a fire. You use the fire to warm yourself and to help you see to read a book. What energy transformation(s) is taking place?

Chemical energy is transformed to light energy and heat energy

You eat a large meal and then hike up a hill. What kind of energy transformation(s) is your body performing?

Chemical energy to kinetic energy and gravitational potential energy

The chart above represents the work output and the time to do the work for four machines. For which machine is the power output least?

II

The chart above represents the work output and the time to do the work for four machines. For which machine is the power output greatest?

IV

The chart above represents the work output and the time to do the work for four machines. Which machine in the table above is the most efficient?

IV

A football player runs to the north at a speed of 8 m/s. He catches a ball and keeps running with the ball. What type of collision was this?

Inelastic (but not perfectly inelastic).

A billiard ball collides with a stationary identical billiard ball in an elastic head-on collision. After the collision, which is true of the first ball?

It comes to rest

A 1300 kg car with 370 kg of passengers and cargo is moving at 72 m/s. Suddenly, the driver applies the brakes and the car skids to a stop. What happens to the momentum that the car (and its contents) had before braking?

It is transferred to the pavement (and the Earth)

Which of the levers shown above has the largest mechanical advantage?

Lever A

Which of the following equipment is the best choice for investigating elastic or nearly elastic collisions?

Marble launcher that causes two marbles to collide with each other.

Which of the following statements about the energy of a pendulum is true?

None of the above are true

The majority of the energy you use everyday can be traced back to what original source?

Nuclear energy in hydrogen atoms released by fusion reactions in the sun

Based on the setup below, which of the following statements is true? (Assume the car starts at rest and there is no friction.)

The car will never reach the egg

A person strikes a ball with a bat. The temperature of the ball increases by 0.06 °C. What accounts for the increase?

The kinetic energy of the moving bat was used to increase the thermal energy of the bal

A student standing motionless on roller skates throws a basketball forward. How does the momentum of the student on skates compare to the momentum of the basketball?

The momentum of the student is equal in magnitude but opposite in direction to the momentum of the basketball

A steel ball traveling at 6 m/s hits a stationary line of three steel balls of the same mass as the original. Which statement is true if the collision is perfectly elastic?

The original ball stops and a single ball moves to the right at 6 m/s.

As a pendulum swings from its highest to its lowest position along an arc, what happens to its kinetic energy and potential energy? Incorrect answer:

The potential energy decreases while the kinetic energy increases

A ball falls from a height h from a tower. Which of the following statements is true?

The sum of the kinetic and potential energies of the ball is a constant

A ball falls from a height h from a tower. Which of the following statements is true?

The sum of the mechanical kinetic and gravitational potential energies of the ball is a constant

A 20 kg shopping cart moving at a velocity of 0.5 m/s collides into a store wall and stops. The momentum of the shopping cart

decreased

Running on a treadmill transforms the chemical energy in the food you eat into

kinetic energy