Edexcel GCSE Physics (1PH0) — Energy – forces doing work
Where:
= work done, or energy transferred, measured in Joules (J)
= force applied, measured in Newtons (N)
= distance moved in the direction of the force, measured in metres (m)
One Joule is defined as the work done when a force of N moves an object through a distance of m in the direction of the force (meaning J = Nm).
If multiple forces act on an object (like a ship's engine pushing forward against water resistance), you must calculate the resultant force to find the work done to accelerate the object.
How do we apply this formula in an exam situation?
A cyclist applies a braking force of N to stop their bike. The bike travels m before coming to a complete stop. Calculate the work done by the brakes.
Step 1: Identify the known values.
Step 2: State the equation and substitute the values.
Step 3: Calculate the final answer with units.
A crane transfers kJ of energy while lifting a steel beam. If the crane applies a steady upward force of N, calculate the vertical distance the beam is lifted.
Step 1: Convert units to standard SI units.
Step 2: Rearrange the equation to make distance the subject.
Step 3: Substitute the values and calculate.
Students often think work is being done when carrying a heavy object horizontally, but because the movement is perpendicular to the upward lifting force, the work done by that lifting force is actually zero.
In Edexcel 'Show that' calculation questions, examiners award a specific mark for showing the substitution of values into the formula; a 'bald' answer with no working will score zero marks.
Always check your units before substituting into the equation — you must convert kilojoules (kJ) to Joules (J) and centimetres (cm) to metres (m) to access full marks.
If a question asks you to describe the energy transfer when a vehicle brakes, explicitly state that energy is transferred from the kinetic store to the thermal store of the brakes and surroundings.
Work done
The amount of energy transferred when a force causes an object to move through a distance.
Mechanical pathway
The specific energy transfer process used when a force moves an object.
System
An object or a group of objects being studied in physics.
Joules (J)
The SI unit of energy; 1 Joule is the work done when a force of 1 Newton moves an object 1 metre in the direction of the force.
Distance moved in the direction of the force
The specific displacement relevant to calculating work done; it excludes any movement at right angles to the applied force.
Resultant force
The single overall force acting on an object when all individual forces are combined.
Power
The rate at which work is done or energy is transferred, measured in Watts (W).
Put your knowledge into practice — try past paper questions for Physics
Work done
The amount of energy transferred when a force causes an object to move through a distance.
Mechanical pathway
The specific energy transfer process used when a force moves an object.
System
An object or a group of objects being studied in physics.
Joules (J)
The SI unit of energy; 1 Joule is the work done when a force of 1 Newton moves an object 1 metre in the direction of the force.
Distance moved in the direction of the force
The specific displacement relevant to calculating work done; it excludes any movement at right angles to the applied force.
Resultant force
The single overall force acting on an object when all individual forces are combined.
Power
The rate at which work is done or energy is transferred, measured in Watts (W).
