5 - Energy & Work - Physics MCAS Practice

An engineer is constructing a device that turns electrical energy into mechanical energy. The engineer notices that some of the electrical energy also turns into thermal energy. Which of the following describes how the device can reach maximum efficiency?

• The device must minimize electrical energy while maximizing thermal

  energy.

• The device must minimize mechanical energy while maximizing thermal

  energy.

• The device must minimize thermal energy while maximizing mechanical

  energy.

• The device must minimize mechanical energy while maximizing electrical

  energy

Tags

NGSS.HS-PS3-3

NGSS.HS-PS3-4

A new power station is being constructed, and the designers claim that it will be extremely efficient. They claim that for every 1,000,000 J of energy that is put into the station 400,000 J of energy will be produced. How efficient is the station?

• 40%

• 60%

• 4%

• 2.5%

Tags

NGSS.HS-PS3-3

If you apply 50 N of work to move something 2 meters, how much work did you do?

• 25 J

• 100 J

• 0.04 J

• 50 J

A 2 kg cart is released from rest from the top of a ramp that is 1 m high. Three positions of the cart are shown in the diagram. Assume friction is negligible.

Which of the following tables correctly shows the cart’s gravitational potential energy and kinetic energy at positions A, B, and C?

• 
• 
• 
• 

Tags

NGSS.HS-PS3-1

NGSS.HS-PS3-2

Some atomic nuclei can be split apart into fragments and other particles, such as neutrons. Once a nucleus is split, fragments move away from each other very quickly. The fragments then slow down as they interact with the surrounding medium. An example of this process is shown in the diagram.

Which of the following describes the energy during this nuclear process?

• The fragments initially have kinetic energy, which is transferred to the surrounding medium as mass.

• The fragments initially have gravitational energy, which is transferred to the surrounding medium as mass.

• The fragments initially have kinetic energy, which is transferred to the surrounding medium as thermal energy.

• The fragments initially have gravitational energy, which is transferred to the surrounding medium as thermal energy.

Tags

NGSS.HS-PS1-8

A student released two objects at rest, W and X, from the same height above the ground. The table shows the masses of the objects and the height from which the student dropped them.

Which of the following describes object W’s kinetic energy just before both objects hit the ground?

• Object W’s kinetic energy was equal to object X’s kinetic energy.

• Object W’s kinetic energy was less than object X’s kinetic energy

• Object W’s kinetic energy was greater than object X’s kinetic energy.

Tags

NGSS.HS-PS3-2

A student released two objects at rest, W and X, from the same height above the ground. The table shows the masses of the objects and the height from which the student dropped them.

Which of the following describes object W’s velocity just before both objects hit the ground?

• Object W’s velocity was one-half of object X’s velocity.

• Object W’s velocity was equal to object X’s velocity.

• Object W’s velocity was two times object X’s velocity.

• Object W’s velocity was four times object X’s velocity.

Tags

NGSS.HS-PS2-1

NGSS.HS-PS2-4

A ball is dropped from the top of the Eiffel Tower. Describe the ball's mechanical energy as it falls.

• The potential energy of the ball is conserved as it falls.

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

• The kinetic energy of the ball is conserved as it falls.

• A) The total energy of the ball increases as it falls since it gains speed.

In which of the following situations is kinetic energy decreasing?

• A ball is dropped from a building.

• A satellite is moving in a circular orbit around the moon.

• A baseball is moving upward after being thrown up in the air.

• An elevator is moving upward at a constant velocity.

Tags

NGSS.HS-PS3-1

NGSS.HS-PS3-2

The graph on the right shows the kinetic energy over time for an object in motion. At time t = 0, the potential energy of the object is 10 J. Determine the potential energy of the object at time t = 9 s.

• 4 J

• 10 J

• 8 J

• 2 J

Tags

NGSS.MS-PS3-1