Energy

Build G2 Science energy reasoning through stores, transfers and conservation, with lessons on kinetic energy, work and power.

SEC G2 Science Physics component 2027
3 lessons

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Before you begin

Energy cannot be made or destroyed, only stored and transferred, so you can follow every joule through a process. The lessons start by naming energy stores and the ways energy moves between them, then calculate kinetic and gravitational potential energy. They finish with the work done by a force and the power of a transfer.

Be comfortable with: kinematics, because kinetic energy depends on speed, and dynamics, because work is done by a force.

Learning goals

Recognise kinetic, potential, nuclear and internal energy stores
Describe mechanical energy transfer by a force acting over a distance
Describe electrical energy transfer by an electric current
Describe energy transfer by heating due to a temperature difference
Describe energy transfer by electromagnetic and mechanical waves
State and apply the principle of conservation of energy
Recall and apply Ek = ½mv² in new situations
Recall and apply Ep = mgh near the Earth's surface in new situations
Recall and apply work done = force × distance moved in the force direction
Recall and apply power = energy transfer / time taken

Syllabus statements covered

show an understanding that there are energy stores, e.g. kinetic, potential (gravitational, chemical, elastic), nuclear and internal, and that energy that can be transferred from one store to another: (i) Mechanically (by a force acting over a distance) (ii) Electrically (by an electric current) (iii) By heating (due to a temperature difference) (iv) By propagation of waves (both electromagnetic and mechanical)
recall and apply the relationships for kinetic energy (Ek = ½mv²) and gravitational potential energy near the Earth's surface (Ep = mgh) to new situations or to solve related problems
state the principle of the conservation of energy and apply the principle to new situations or to solve related problems
recall and apply the relationship work done = force × distance moved in the direction of the force to new situations or to solve related problems
recall and apply the relationship power = energy transfer / time taken to new situations or to solve related problems

Lessons

Work through them in order.

Practise and check

Topic reference

Quick reference

Quantity	Relationship	Unit
kinetic energy	Eₖ = (1/2)mv²	joule, J
gravitational potential energy	Eₚ = mgh, with g = 10 N/kg	joule, J
work done	work done = force × distance moved in the direction of the force	joule, J
power	power = energy transferred ÷ time taken	watt, W

Way energy is transferred	Example
mechanically	a force moving an object through a distance
electrically	an electric current in a circuit
by heating	from a hot object to a cooler one
by waves	light from the Sun, sound from a speaker

Core knowledge to remember

Energy is held in stores, such as kinetic, gravitational potential, chemical, elastic, nuclear and internal, and is transferred between stores mechanically, electrically, by heating or by waves.
Principle of conservation of energy: energy cannot be created or destroyed; it can only be transferred from one store to another. The total energy stays the same.
Work done = force × distance moved in the direction of the force.
Power = energy transfer ÷ time taken.

Common mistakes

Saying energy is used up. It is transferred, often to the internal energy of the surroundings.
Using a mass in grams, or a height that is not vertical, in Eₖ = (1/2)mv² or Eₚ = mgh.
Forgetting to square the speed in (1/2)mv².
Using a distance that is not in the direction of the force when calculating work done.
Using time in minutes instead of seconds when calculating power.