Lecture 2.5: Circular motion

Question 1

what is angular displacement?

Answer 1

the distance in radians that an object has rotated through
θ = s/r
where s is arc distance

Question 2

how to convert between radians & degrees?

Answer 2

radian = degrees x 2π/360
degrees = radian x 360/2π

Question 3

define angular velocity
formulae

Answer 3

rate at which angular displacement changes
ω = v/r
measured in radian s^-1
θ = ωt
ω = 2πf - relationship between angular velocity & freq.

Question 4

define period and give a formula for velocity using period

Answer 4

time taken to do one complete rotation of a circular path
v = 2πr / T

Question 5

explain acceleration, force and velocity in circular motion

Answer 5

velocity of an object in circular motion changes due to change in direction
velocity is always tangential to circle
if object is travelling at constant speed, acceleration is always towards the centre of the circular path (ac = v^2/r)
as there is acceleration there is a net force produced towards the centre of the circle (Fc = mv^2/r)