OCR A-Level Physics B H557
Planning
Implementing
Analysis
Evaluation
Practical Skills
Use of Apparatus and Techniques
Fundamental Data Analysis
Imaging and Signalling
Sensing
Mechanical Properties of Materials
Waves and Quantum Behaviour
Space, Time and Motion
Creating Models
Out Into Space
Our Place in the Universe
Matter: Very Simple
Matter: Hot or Cold
Electromagnetism
Charge and Field
Probing Deep Into Matter
Ionising Radiation and Risk
Space, Time and Motion
Work, energy and its conservation
- 3 things to know
- Components 01, 02 and 03
Overview
Recall questions on work done ΔE = FΔs and FΔs cos θ, forces at right angles to motion, the joule, conservation of energy, kinetic energy Eₖ = ½mv² and gravitational potential energy mgh with calculations, the landing speed v = √(2gh), why doubling speed quadruples kinetic energy, braking, and energy lost to friction.
What you need to know
Answer each one before you reveal it.
Define the work done by a force.
State the equation for work done when the force is parallel to the displacement.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Define the work done by a force.
Model answer
Work done is the product of the force and the distance moved in the direction of that force.
- 2
State the equation for work done when the force is parallel to the displacement.
Model answer
The work done is ΔE = FΔs.
- 3
State the equation for work done when the displacement is at an angle θ to the force.
Model answer
The work done is ΔE = FΔs cos θ.
- 4
Why is no work done by a force that acts at right angles to the motion?
Model answer
cos 90° is zero, so there is no displacement in the direction of that force and it transfers no energy.
- 5
A crate is dragged 12 m across a floor by a rope pulling with a force of 80 N at 30° to the horizontal. What is the work done by the rope?
Model answer
ΔE = FΔs cos θ = 80 × 12 × cos 30° = 8.3 × 10² J.
- 6
Define the joule.
Model answer
One joule is the energy transferred when a force of one newton moves its point of application one metre in the direction of the force.
Other ways to work this
The same content, four other ways.
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Six ways to work the same material.
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