Work and Kinetic Energy Practice

A net force acts on an object. Which of the following must be true? (SELECT ALL THAT APPLY.)

• The object accelerates.

• The object's velocity changes.

• Net work is done on the object.

• The object's kinetic energy changes.

Tags

NGSS.HS-PS2-1

Why does kinetic friction always do negative work on a sliding object?

• Kinetic friction always points in the direction opposite to an object's velocity, slowing it down and transferring energy from the object to the environment.

• Kinetic friction always points in the same direction as an object's velocity, slowing it down and transferring energy from the object to the environment.

• Kinetic friction always points in the direction opposite to an object's velocity, slowing it down and transferring energy from the environment to the object.

• Kinetic friction always points in the same direction as an object's velocity, slowing it down and transferring energy from the environment to the object.

Which of the following is true about the work done on an object by gravity?

• Gravity always does positive work on an object that moves downward.

• Gravity always does negative work on an object that moves downward.

• Gravity always does no work on an object that moves downward.

• Gravity sometimes does positive work on an object that moves down.

Tags

NGSS.HS-PS2-4

In which of the following scenarios does tension do positive work? (SELECT ALL THAT APPLY.)

• A rope is used to pull a bucket of water up a well.

• A cord is attached to a stationary box on a flat surface and pulled at an angle to drag it away.

• A rope is attached to the back of a car that's rolling downhill in order to try to slow it down, but there's not enough force to prevent the car from speeding up as it rolls.

• One side of a string is fixed in place while the other side is attached to a yo-yo. After a gentle push, the yo-yo swings back and forth.

Tags

NGSS.HS-PS3-2

An object is slowing down. What can be concluded?

• The sum of work done by each force acting on the object is negative.

• The angle between the net force on the object and object's displacement is acute.

• No force is doing positive work on the object.

• The angle between the net force on the object and the object's displacement is 180 degrees.

An object is released at rest on a frictionless inclined plane, after which it slides down the inclined plane. Which of the following is true while the object is sliding? (SELECT ALL THAT APPLY.)

• Only gravity does work on the object.

• The angle between the normal force on the object and the object's displacement is 90 degrees.

• Both gravity and normal force do work on the object.

• The angle between the object's weight and displacement is obtuse.

Tags

NGSS.HS-PS2-1

An object is dropped off a cliff of height h. Ignoring air resistance, what does the work-kinetic energy state about the object's speed, v_f, when it hits the ground? (SELECT ALL THAT APPLY.)

• W_g = K_f

• gh = v_f²/2

• ΔK > 0

• W_g > 0

An object is thrown straight upward. What does a graph of it's kinetic energy look like as the object moves upward, reaches its maximum height, then comes back downward?

• Parabola with a minimum

• Parabola with a maximum

• Line with a negative slope

• Line with a positive slope

An object experiences two forces, F₁ and F₂, and moves with constant speed. What can be concluded?

• W₁ = -W₂

• W₁ = W₂ = 0

• F₁ = F₂ (magnitudes)

• ΣF = 0

Tags

NGSS.HS-PS2-2

How much work does gravity do on a 2-kg object that's thrown upward to a maximum height of 10 m?

• -196 J

• 196 J

• 0 J

• 98 J

• -98 J