Ch16 circular motion

Question 1

Converging between radians and degrees?

Answer 1

D to R = x pi/180
R to D = x 180/pi

Question 2

What do you know about velocity in circular motion?

Answer 2

• Speed is constant
• Velocity is changing as the direction of v changes.

Question 3

Why is speed constant if there is a force acting?

Answer 3

• F is acting towards the centre.
• V is perpendicular to F.
• hence there is no work done,
  as W = Fdcosθ, θ=90,
  W = 0
• hence the speed is constant.

Question 4

What do you know about centripetal acceleration?

Answer 4

• a is acting towards the centre.
• a is changing as V is changing.
• centripetal acceleration = V^2 / r

Question 5

what do you know about centripetal force.

Answer 5

it’s a resultant force that acts perpendicular to the direction of motion
- F is acting towards the centre
- F =ma
hence F =mv^2 / r

Question 6

angular velocity?

Answer 6

-angular velocity = ω
ω = θ / t
unit = rads^-1

Question 7

rpm to rads^-1

Answer 7

rpm to rads^-1:
rpm x2pi /60

Question 8

Circular motion at an angle

Answer 8

Car turning at a banked surface.
Ry =mg
Ry = Rcosθ
Rcosθ =mg

Rx = Fc = mv^2/r
Rx = Rsinθ
Rsinθ = mv^2/r

Question 9

Vertical circular motion

Answer 9

• Tension always acting towards the centre.
• Weight always acting down.
  1(at the top):
• F=ma
• T1+mg=mv^2/r
• T1=mv^2/r-mg

2(at the bottom):
- F=ma
- T2-mg=mv^2/r
- T2=mv^2/r+mg