Circular Motion

Question 1

define time period

Answer 1

time taken for an object to turn through a complete circle

Question 2

define frequency

Answer 2

number of revolutions per unit time

Question 3

define angular velocity

Answer 3

angular displacement per unit time

Question 4

define centripetal acceleration

Answer 4

acceleration of an object in a steady circular path toward the centre of a circle at 90’ to object’s linear velocity

Question 5

define centripetal force

Answer 5

a force causing an object to move in a circular path, acts toward centre of circle

Question 6

how do aerofoils help cars travel around corners without skidding?

Answer 6

asymmetric curved shape makes air flow faster below aerofoil than above so air pressure lower below aerofoil, therefore downward force on aerofoil and car which increases amount of lateral friction therefore increasing size of centripetal force

Question 7

how do you calculate the lateral friction required to prevent a car from skidding?

Answer 7

friction = centripetal force (mv^2)/r

Question 8

in a conical pendulum, what are the two components of tension equal to weight and centripetal force; and equation for theta(0)?

Answer 8

Tsin0 = (mv^2) / r

Tcos0 = mg

tan0 = v^2 / rg

Question 9

how does banking tracks make curving easier and allow for greater speeds?

Answer 9

Components of normal reaction force and and lateral friction contribute to centripetal force; although contribution from lateral friction slightly reduced, more than compensated for by extra contribution from normal reaction force

Question 10

calculate maximum sped that bobsleigh could travel around a curve with radius r and without exceeding banking angle 0?

Answer 10

1. assume ice contributes no lateral friction: mv^2 /r = Nsin0 (Fcos0 removed)
2. tan0 = v^2 / rg, hence
   v = (rgtan0)^1/2

Question 11

how do aircrafts use banking in order to change direction?

Answer 11

lift force no longer just acting in vertical direction, horizontal component of lift force creates a resultant force towards the centre circle and provide centripetal force

Question 12

write an equation for the centripetal force of a car at the top of a hill?

Answer 12

mv^2 / r = mg - R

Question 13

write an equation for the centripetal force of a rollercoaster cart at the top and bottom of its path?

Answer 13

top: mv^2 /r = mg + R
bottom: mv^2 /r = R - mg

Question 14

why are clothes swung to side of dryer?

Answer 14

nothing to provide centripetal force so just move tangentially until they hit side of drum

Question 15

what does 1 tonne equal?

Answer 15

1000kg

Question 16

write an equation for centripetal force of a mass attached to string, travelling in a vertical circle, at the top and bottom of its path?

Answer 16

top: mv^2 /r = mg + T

bottom : mv^2 /r = T - mg