OCR A-Level Physics A H556
Practical Skills in the Written Papers
The Practical Endorsement
Physical Quantities and Units
Making Measurements and Analysing Data
Nature of Quantities
Motion
Forces in Action
Work, Energy and Power
Materials
Newton’s Laws of Motion and Momentum
Charge and Current
Energy, Power and Resistance
Electrical Circuits
Waves
Quantum Physics
Thermal Physics
Oscillations
Gravitational Fields
Astrophysics and Cosmology
Capacitors
Electric Fields
Electromagnetism
Nuclear and Particle Physics
Work, Energy and Power
Work done and conservation of energy
- 2 things to know
- Papers 1 and 3
Overview
Recall questions on work done and its unit, W = Fx cos θ and calculations with it, the principle of conservation of energy, forms of energy and how energy transfer relates to work done.
What you need to know
Answer each one before you reveal it.
What is the definition of work done in physics?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is the definition of work done in physics?
Model answer
Work done is the energy transferred when a force moves an object through a distance in the direction of the force.
- 2
What is the SI unit of work done, and how is it defined in base units?
Model answer
The SI unit of work done is the joule (J), where 1 joule equals 1 newton metre, which is 1 kg m² s⁻² in base units.
- 3
State the equation used to calculate work done when a force acts at an angle to the displacement.
Model answer
W = Fx cos θ, where F is the force, x is the displacement, and θ is the angle between the force and displacement vectors.
- 4
In the equation W = Fx cos θ, what does the angle θ represent?
Model answer
θ is the angle between the force vector and the displacement vector.
- 5
Why is the cosine function used when calculating work done by a force at an angle?
Model answer
The cosine function gives the component of the force acting in the direction of the displacement, since only this component does work.
- 6
Calculate the work done when force = 54 N, displacement = 88.9 m, angle = 38°.
Model answer
Work done = 54 × 88.9 × cos 38° = 3780 J.
Other ways to work this
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