Unit 4: Energy

AP Physics 1: Algebra-Based

Unit 4 Key Info

• Kinetic energy: KE = 1/2mv^2

• Potential energy: PE = mgh

• Work-energy theorem: Wnet = ΔKE = KEf - KEi

• Conservation of mechanical energy: KEi + PEi = KEf + PEf

• Power: P = W/t

• Law of conservation of energy: Energy cannot be created or destroyed, only transferred or transformed.

What is work?

Work is the transfer of energy that occurs when a force is applied over a distance.

What is the formula for work?

The formula for work is W \= Fd, where W is work, F is force, and d is distance.

What is the unit of measurement for work?

Work is measured in joules (J).

What happens when the force is applied at an angle in relation to the intended distance of travel?

The formula for work becomes W \= Fd cos θ.

What is mechanical energy?

Mechanical energy is the sum of kinetic energy and potential energy in a system.

What is kinetic energy?

Kinetic energy is the energy of motion and is given by the formula KE \= 1/2mv^2, where m is mass and v is velocity.

What is potential energy?

Potential energy is the energy stored in an object due to its position or configuration and is given by the formula PE \= mgh, where m is mass, g is acceleration due to gravity, and h is height.

Is mechanical energy conserved in a closed system?

Yes, mechanical energy is conserved in a closed system, meaning that the total amount of mechanical energy remains constant.

What is the work-energy theorem?

The work-energy theorem states that the net work done on an object is equal to the change in its kinetic energy.

What is the formula for the work-energy theorem?

The formula for the work-energy theorem is Wnet \= ΔKE, where Wnet is the net work done on an object and ΔKE is the change in its kinetic energy.

What is the sum of an object’s kinetic energy and potential energies called?

The sum of an object’s kinetic energy and potential energies is called its total mechanical energy.

Is the conservation of mechanical energy valid for systems with nonconservative forces?

The equation Ki + Ui \= Kf + Uf holds if no nonconservative forces are doing work. However, if work is done by such forces during the process under investigation, then the equation needs to be modified to account for this work as follows: Ki + Ui + Wother \= Kf + Uf.

What is power?

Power is the rate at which work is done or energy is transferred. It is a scalar quantity and is measured in watts (W).

What is the formula for power?

The formula for power is P \= W/t, where P is power, W is work, and t is time.

What is the unit of measurement for power?

The SI unit for power is watts (W).

What is the relationship between power and energy?

Energy is the ability to do work, while power is the rate at which work is done. The amount of energy used depends on both the power and the time it is used for.

What is efficiency?

Efficiency is a measure of how much of the input energy is converted into useful output energy.

What is the formula for efficiency?

The efficiency of a device can be calculated using the formula: efficiency \= useful output energy / input energy.

How is power related to efficiency?

Power is also related to efficiency. The higher the power output of a device, the more ene