Physics AS Level - Energy, Work and Power

Flashcards about Energy Conversion and Conservation, Work and Efficiency, Potential Energy and Kinetic Energy, and Power.

What is the principle of conservation of energy?

Energy cannot be created or destroyed, it can only change from one form to another.

What happens to the total amount of energy in a closed system?

It remains constant, although how much of each form there is may change.

Give an example of energy transformation in a falling object (in a vacuum).

Gravitational potential energy transforms into kinetic energy.

Give an example of energy transformation in a battery.

Chemical energy transforms into electrical energy, which can then transform into light energy (if connected to a bulb).

Give an example of energy transformation in a horizontal mass on a spring.

Elastic potential energy transforms into kinetic energy.

What is kinetic energy?

Energy of a moving object.

What is gravitational potential energy?

Energy something gains when you lift it up, and which it loses when it falls.

What is elastic potential energy?

Energy of a stretched spring or elastic band (sometimes called strain energy).

What is chemical energy?

Energy contained in a chemical substance.

What is nuclear energy?

Energy contained within the nucleus of an atom.

What is internal heat energy?

Energy something has due to its temperature (or state). (Sometimes referred to as thermal or heat energy)

What does dissipation refer to in energy transfers?

Ways in which energy is wasted.

What forms do wasted energy usually take?

Thermal (heat), light, or sound energy.

Define work in physics.

Work is done when an object is moved over a distance by an external force applied in the direction of its displacement.

What is the relationship between work and energy transfer?

When work is done, energy is transferred from one object to another.

In what units is work measured?

Joules (J).

What happens to an object's energy if a force acts in the direction it is moving?

The object will gain energy.

What happens to an object's energy if a force acts in the opposite direction to its movement?

The object will lose energy.

When does a gas do work on its surroundings?

When a gas expands, it does work on its surroundings by exerting pressure on the walls of the container.

Write the formula that represents the work done by a gas.

W = pΔV

What is efficiency of a system?

The efficiency of a system is the ratio of the useful energy output from the system to the total energy input.

What is the result of a system with high efficiency?

Most of the energy transferred is useful.

What is the result of a system with low efficiency?

Most of the energy transferred is wasted.

How is efficiency expressed as a percentage?

efficiency = (useful energy output / total energy input) x 100

Write the formula that represents the efficiency in terms of power.

efficiency = (useful power output / total power input) x 100

What is kinetic energy?

Kinetic energy is energy an object has due to its motion (or velocity).

Write the formula for kinetic energy.

Ek = (1/2)mv²

What happens to kinetic energy when an object is falling?

When an object is falling, it is gaining kinetic energy since it is gaining speed. This energy is transferred from the gravitational potential energy it is losing.

What is gravitational potential energy (GPE)?

Gravitational potential energy (GPE) is the energy stored in an object that is held at a height above the Earth's surface.

Write the formula fo gravitational potential energy.

Ep = mgh

What is elastic potential energy (EPE)?

Elastic potential energy (EPE) is the energy stored in objects when they are stretched or compressed.

What is power?

The power of a machine is the rate at which it transfers energy.

What is the SI unit for power?

Watts (W) where 1 W = 1 J s⁻¹

Write the formula for power.

P = W/t = ΔE/t = Fv