5.2 Circular Motion

Question 1

recall how to convert from radians to degrees, and vice versa

Answer 1

1 radian = 180/π degrees
1 degree = π/180 radians

Question 2

recall the equation for linear velocity

Answer 2

v=ωr

Question 2

recall the equations for angular velocity

Answer 2

ω=2π/T, ω=2πF

Question 3

define frequency and period, and recall their relationship

Answer 3

frequency: no. rotations per second
period: time taken for one complete rotation
f=1/t, t=1/f

Question 4

recall the equations for centripetal acceleration

Answer 4

a=v²/r, a=ω²r

Question 5

recall the equations for centripetal force

Answer 5

f=mv²/r, f=mω²r

Question 6

define centripetal acceleration and centripetal force

Answer 6

acceleration and force acting towards the center of the circle (direction is constantly changing = acceleration = res force)

Question 7

discuss work done by the centripetal force

Answer 7

there is no work done, as the distance from the center is constant, no energy is lost from the centripetal force

Question 8

describe banked tracks

Answer 8

outside edge is higher than the inside, so any friction acts up/down the slope depending on the cars tendency to slip up/down, this opposes motion

Question 9

describe a PAG to investigate circular motion

Answer 9

• tie a bung of mass m to a piece of string
• thread it through a glass tube
• mark where string meets tube
• suspend a weight of mass M from the other end
• F = Mg (tension in string is constant)
• whirl string in a circle, record time taken for ten complete rotations (divide by ten)
• alter the weight of the mass and repeat the experiment
• measure radius with a ruler

centripetal force = mv²/r, weight of mass = Mg, ∴ Mg=mv²/r

plot a graph of v² against M, a straight line graph which passes through the origin should be produced