AP Physics 1 work-energy theorem practice questions

Define work in physics.

Work is defined as the product of the force applied to an object and the distance over which that force is applied in the direction of the force: $\displaystyle W = F imes d imes ext{cos}( heta)$.

True or False: Work can be negative.

True. Work is negative when the force and displacement are in opposite directions.

What is kinetic energy?

Kinetic energy (KE) is the energy of an object due to its motion, given by the formula: $\displaystyle KE = \frac{1}{2} mv^2$.

Fill in the blank: Potential energy is the energy stored due to an object's _____.

position or configuration.

Compare kinetic energy and potential energy.

Kinetic energy depends on motion; potential energy depends on position. Both forms are interconvertible.

What is the unit of work?

The unit of work is the Joule (J), defined as one Newton-meter (N·m).

Cause → Effect: What happens when work is done on an object?

The object's energy increases; it may speed up or change position.

Calculate the work done: 50 N force over 10 m in direction of force.

Work = 50 N × 10 m = 500 J.

What is gravitational potential energy?

Gravitational potential energy (PE) is energy stored due to an object’s height: $\displaystyle PE = mgh$.

True or False: All systems maintain the same amount of kinetic energy.

False. Kinetic energy varies based on an object's velocity.

Define mechanical energy.

Mechanical energy is the sum of kinetic and potential energy in a system: $\displaystyle ME = KE + PE$.

What does the work-energy theorem state?

The work-energy theorem states that the work done on an object equals the change in its kinetic energy: $\displaystyle W = riangle KE$.

Calculate kinetic energy of a 2 kg object moving at 3 m/s.

$\displaystyle KE = \frac{1}{2} (2 ext{ kg}) (3 ext{ m/s})^2 = 9 ext{ J}$.

Fill in the blank: The work done by a force is maximum when the angle is _____.

0 degrees.

True or False: Potential energy can only exist in gravitational fields.

False. Potential energy can exist in various fields, including electric and magnetic.

What affects the potential energy of an object?

The height above a reference point and the mass of the object influence potential energy.

A 2 kg object is dropped. What is its kinetic energy at 10 m?

Using $\displaystyle KE = \\frac{1}{2}mv^2$. At 10 m, $\displaystyle v = \sqrt{2gh} = \sqrt{2(9.81)(10)} \approx 14 m/s$. Therefore, $\displaystyle KE = \\frac{1}{2}(2)(14^2) = 196 J.$

True or False: Work done by friction is positive.

False. Work done by friction is negative as it opposes motion, reducing kinetic energy.

Calculate work done if a force of 50 N moves an object 4 m.

Work $\displaystyle W = F \cdot d = 50 N \cdot 4 m = 200 J$.

Potential energy formula involves which two quantities?

Mass (m) and height (h): $\displaystyle PE = mgh$.

Fill in the blank: When work is done on an object, its __________ changes.

energy.

A car travels up a hill. What happens to its kinetic energy?

Kinetic energy decreases as potential energy increases, due to work done against gravity.

Compare gravitational potential energy and kinetic energy.

- $\displaystyle PE = mgh$ - $\displaystyle KE = \\frac{1}{2}mv^2$ - Potential energy is stored; Kinetic energy is in motion.

A spring is compressed. How is work related to potential energy?

Work done to compress the spring becomes elastic potential energy: $\displaystyle PE = \\frac{1}{2}kx^2$.

A 3 kg ball rolls down a ramp. What energy conversions occur?

Potential energy converts to kinetic energy as it rolls down.

How does doubling speed affect kinetic energy?

Kinetic energy increases by a factor of four: $\displaystyle KE = \\frac{1}{2}m(2v)^2 = 2mv^2$.

True or False: Work-Energy Theorem states total work equals change in kinetic energy.

True. $\displaystyle W_{total} = \Delta KE$.

A 5 kg box is pushed with 30 N over 6 m. Find work done.

$\displaystyle W = F \cdot d = 30 N \cdot 6 m = 180 J$.

Conservation of Mechanical Energy states what?

The total mechanical energy (kinetic + potential) in a closed system remains constant, provided only conservative forces act.

True or False: Total energy can be created or destroyed.

False: According to the law of conservation of energy, energy cannot be created or destroyed, only transformed.

Fill in the blank: In an ideal system, __________ energy is converted to kinetic energy.

Potential energy.

What happens to potential energy as an object falls?

It decreases while kinetic energy increases, keeping total mechanical energy constant.

Compare kinetic energy (KE) and potential energy (PE).

- KE: Energy of motion - PE: Energy due to position or configuration

Example: A 2 kg object is 5 m high. Calculate its PE.

PE = mgh = (2 kg)(9.81 m/s²)(5 m) = 98.1 J.

What is the total mechanical energy at the highest point of a swing?

Total mechanical energy equals potential energy at the highest point since kinetic energy is zero.

True or False: Non-conservative forces do not affect total mechanical energy.

False: Non-conservative forces (like friction) dissipate energy as heat, reducing total mechanical energy.

What is the formula for gravitational potential energy?

PE = mgh, where m = mass, g = acceleration due to gravity, h = height.

Cause → Effect: If an object's height increases, what happens to its PE?

Its potential energy increases.

Identify the term: Energy stored in an object's position.

Potential energy.

Determine KE: A 3 kg object moving at 4 m/s.

KE = \frac{1}{2}mv^2 = \frac{1}{2}(3 kg)(4 m/s)^2 = 24 J.