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
Kinetic and gravitational potential energy
- 4 things to know
- Papers 1 and 3
Overview
Recall questions on kinetic energy and gravitational potential energy, their equations, calculations and derivations from first principles, and the exchange between them for a freely falling object.
What you need to know
Answer each one before you reveal it.
When an object is lifted through a height h at constant velocity, what force is needed, how is the work done calculated, and what happens to that work?
In deriving the kinetic energy equation from first principles, what two equations do you start with?
What is kinetic energy?
Questions from this subtopic
Each one with the model answer underneath.
- 1
In deriving the kinetic energy equation from first principles, what two equations do you start with?
Model answer
W = Fx (definition of work done) and F = ma (Newton's second law).
- 2
For an object accelerating from rest, how does the work done relate to kinetic energy in the derivation?
Model answer
When u = 0, the work done equals the kinetic energy gained: Eₖ = ½mv².
- 3
What is kinetic energy?
Model answer
Kinetic energy is the energy an object possesses due to its motion.
- 4
State the equation for calculating kinetic energy and define each term.
Model answer
Eₖ = ½mv², where m is mass and v is velocity.
- 5
Calculate the kinetic energy when mass = 108.1 kg, velocity = 34.2 m/s.
Model answer
Kinetic energy = 0.5 × 108.1 × 34.2 × 34.2 = 63200 J.
- 6
When deriving Eₖ = ½mv², how is the equation v² = u² + 2ax rearranged to express displacement?
Model answer
It is rearranged to give x = (v² − u²)/(2a).
Other ways to work this
The same content, four other ways.
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