Unit 5: Applied

Question 1

What is a rotating system

Answer 1

When an object is spinning on its axis

Question 2

What is meant by the term angular velocity

Answer 2

The angle an object passes through per second

Question 3

What is the most commonly used way of expressing rate of turning

Answer 3

Revolutions per minute

Question 4

How does one convert rpm to radians per second

Answer 4

2pi(rpm/60) = angular velocity

Question 5

What is meant by angular displacement

Answer 5

The angle turned in a given direction.

Question 6

What is the equation linking angular velocity and displacement

Answer 6

omega = theta/t

where omega = angular velocity, theta = angular displacement, t = time

Question 7

What is the equation linking acceleration (angular) and angular velocity

Answer 7

alpha = deltaTheta/deltat

where alpha = angular acceleration

Question 8

What is meant by moment of inertia

Answer 8

MoI is the measure of the opposition of a rotating body to angular acceleration

Question 9

What are the units for moment of inertia

Answer 9

kgm^2

Question 10

What is the equation for inertia

Answer 10

I=sigma*mr^2

I = inertia, m = mass, r = distance from centre of point

Question 11

How does one derive the moment of inertia equation

Answer 11

• Know that a spinning body is made of point masses
• Using Ke = 0.5mv^2, the total kinetic energy can be found by taking the sum of the point massesthe distance from centre^2 all times angular velocity
• Simplyfy

Question 12

What is the equation for the kinetic energy of a spinning object

Answer 12

Ek = (I*omega^2)/2

Where Ek = kinetic energy, I = Inertia, omega = angular velocity

Question 13

What are the equations of rotational motion

Answer 13

Same as suvat replacing u, v and a with omega 1,2 and alpha

Question 14

What is Torque

Answer 14

Any turning force

Question 15

What is the equation for torque in relation to force

Answer 15

T = Fr
T = force, F = force,  r = radius

Question 16

What are the rotational motion versions of:

• Displacement
• Velocity
• Acceleration
• Mass
• Force

Answer 16

• Angular displacement
• Angular velocipede
• Angular acceleration
• Moment of inertia
• Torque

Question 17

How does one calculate torque taking into account the shape of the pulley, and explain how it takes this into account

Answer 17

T = I*alpha

Using inertia to take account for how the mass of the pulley is distributed

Question 18

How does one calculate angular momentum

Answer 18

L = I*omega
L= angular momentum, I = inertia, omega = angular velocity

Question 19

What are the units for angular momentum

Answer 19

kgm^2s^-1

Question 20

What is meant by the conservation of angular momentum

Answer 20

before = momentum after

provided there is no angular impulse

Question 21

What is the equation for angular impulse

Answer 21

(deltaL) = T(delta*t)

Question 22

What equation is used to calculate work done by a rotating system

Answer 22

W = T*theta

Question 23

Equation for power in a rotational system?

Answer 23

P=T*omega

Question 24

How is “angular” friction treated

Answer 24

as an opposing rotational couple which provides a torque in the opposite direction using T = I*alpha