Rotational Motion

Question 1

Rotational (Spinning) Motion vs Circular (Orbital) Motion

Answer 1

Rotational (spinning)

• each position on a spinning object is rotating with a different radius to an adjacent position

E.g. Skater spinning

Circular (orbital)

• rotating object stays a fixed distance (radius) from centre of rotation

E.g. Satellite orbiting earth

Question 2

2x Types of movement

Answer 2

1. Pure rotational

2. Pure translational

Question 3

What is pure rotational movement?

Answer 3

Movement of C.O.M

Without any rotation about the C.O.M

Question 4

What causes pure translational motion?

Answer 4

A force acting through the C.O.M

Question 5

What is Pure rotational motion?

Answer 5

Circular movement around the C.O.M

C.O.M is stationary

Question 6

What causes pure rotational motion?

Answer 6

• force couple
• 2x = & opposite forces some perpendicular distance away from each other
• not necessary for 2 forces to be - distances from the C.O.M

Question 7

Angular displacement

Answer 7

θ - dimensionless unit

Radians - simple relationship between the distance d travelled around the arc of the circle radius r

θ = d/r

Question 8

Angular velocity

Answer 8

ω

How quickly an object rotates

ω = θ/t

Question 9

Relationship between ω and v

Answer 9

ω = v/r

v = ωr

Question 10

Relationship between a and α

Answer 10

a = rα

Question 11

Angular acceleration

Answer 11

α =