AQA A-Level Physics 7408
Measurements and Their Errors
Particles and Radiation
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Further Mechanics and Thermal Physics
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Engineering Physics
Torque and angular acceleration
- 3 things to know
- Paper 3, section B
Overview
Torque as the rotational analogue of force, and T = Iα.
What you need to know
Answer each one before you reveal it.
What do the terms in T = Iα mean, and how does it parallel F = ma?
What unit does torque take, what does a net torque cause, and what does r mean in T = Fr?
Questions from this subtopic
Each one with the model answer underneath.
- 1
State the formula for torque in terms of force and perpendicular distance.
Model answer
T = Fr, where T is torque, F is force, and r is perpendicular distance from the axis of rotation.
- 2
Define torque in words.
Model answer
Torque equals the product of force and the perpendicular distance from the axis of rotation.
- 3
Calculate the torque when force = 144 N, perpendicular distance = 1.28 m.
Model answer
Torque = 144 × 1.28 = 184 N m.
- 4
State the equation relating torque to moment of inertia and angular acceleration.
Model answer
T = Iα, where T is torque, I is moment of inertia, and α is angular acceleration.
- 5
Define each term in the equation T = Iα.
Model answer
T is torque (N m), I is moment of inertia (kg m²), and α is angular acceleration (rad s⁻²).
- 6
Calculate the torque when moment of inertia = 14.5 kg m², angular acceleration = 7 rad s⁻².
Model answer
Torque = 14.5 × 7 = 102 N m.
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