Uniform circular motion

Question 1

When is an object in uniform circular motion?

Answer 1

an object rotating at a steady rate

Question 2

Why is 360 degrees 2π radians?

Answer 2

• arc length = 2πr
• 2πr / r = 2π
• so there are 2π radians in a complete circle

Question 3

What is angular speed?

Answer 3

• ω
• angular displacement per unit time

Question 4

What is the frequency of rotation?

Answer 4

1 / T

where T is time for rotation

Question 5

Why are objects travelling in circles always acceletating?

Answer 5

• velocity always changing
• even when going at constant speed
• changing direction

Question 6

Why is it called centripetal acceleration?>

Answer 6

• always directed towards the centre of the circle

Question 7

What is angular displacement?

Answer 7

the angle an object in circular motion turns through = 2πft = 2πt/T

Question 8

What is centripetal force?

Answer 8

• the resultant force on an object moving around a circle at constant speed
• acts in same direction as centripetal acceleration
• e.g. tension in a string
• causes centripetal acceleration