Rotational dynamics

Question 1

Define torque

Answer 1

A measure of the force that causes an object to rotate

Question 2

Define moment of inertia

Answer 2

The tendency of an object to resist angular acceleration

Question 3

Define Angular momentum

Answer 3

The product of an object’s moment of inertia and angular velocity relative to its axis of rotation

Question 4

State the principle of conservation of angular momentum

Answer 4

The angular momentum of a system is conserved when the net external torque= 0 (isolated system)

Question 5

What are the conditions for a rigid body to be in Equilibrium?

Answer 5

Neither its translational nor rotational motion changes
Meaning translational & angular acceleration = 0
- Fnet =0
- Tnet =0

Question 6

What does the magnitude of torque depend on?

Answer 6

Where and in what direction the force is applied
Location of axis of rotation

Question 7

What are the conditions for maximum torque?

Answer 7

Force is applied perpendicular to lever arm
Force is applied far away from axis of rotation

Question 8

What are the conditions for zero torque?

Answer 8

Force is applied parallel to lever arm
Force is applied directly to axis of rotation
No force is applied
Constant angular velocity thus, angular acceleration =0 and F=0

Question 9

Discuss the differences in moment of inertia when the axis is on one end and when it is in the centre

Answer 9

At one end : I= ml^2
At centre : I =1/2 ml^2

Question 10

What happens to a system where angular momentum (L) is conserved and there is a change in the radius?

Answer 10

Increasing radius(r^2) = increase moment of inertia(I) = decreased angular velocity (w)
E.g when a skater stretches out their arms to slow down