Work energy and power

Definition of work.

Work is the product of the displacement and the component of the force parallel to the displacement.

Definition of gravitational potential energy.

Gravitational potential energy is the energy an object possesses due to its position relative to a reference point.

Definition of kinetic energy.

Kinetic energy is the energy an object has as a result of its motion.

Definition of mechanical energy.

Mechanical energy is the sum of an object's gravitational potential energy and kinetic energy at a point.

Definition of the principle of conservation of mechanical energy.

In the absence of air resistance or any external forces, the mechanical energy of an object is constant.

Definition of the law of conservation of energy.

The total energy in a system cannot be created or destroyed. It can only be transformed from one form to another.

Definition of the work-energy theorem.

The work done by a net force on an object is equal to the change in kinetic energy of the object.

Definition of power.

Power is the rate at which work is done, or the rate at which energy is transferred.

Definition of one watt.

One watt is the power when one joule of work is done in one second.

Definition of efficiency.

Efficiency is the ratio of output power to input power.

If an object gains energy under the action of a force, what is work?

Work is positive.

If an object loses energy under the action of a force, what is work?

Work is negative.

What are the conservative forces?

• Gravitational force

• Elastic / spring force

• Electrostatic force

What are the non conservative forces?

• Friction

• Air resistance

• Applied forces

• Tension in some non-ideal contexts

Non formula sheet work energy and power formulae