Question

25.1) Consider two identical cars travelling around a circular track. One car travels on an inside track and one on an outside track. Both cars complete a lap in the same amount of time. Which car has the highest kinetic energy? A) The outer car B) The inner car C) Both have the same KE 25.2) A solid disk and a flywheel (hoop) both have the same mass m, radius R, and angular velocity w. Which object has more kinetic energy? A) The disk B) The flywheel (hoop) C) Both have the same KE Solid disk of mass m Hoop of mass m and radius R and radius R 3

Answer 1

25.1) angular velocity of both the cars are equal as both takes same time to complete the circle.( )

2 = م T

But liners velocity of outer car is greater because it moves in a circle of greater radius. ($v= \omega r$)

As kinetic energy is given by

K = (1/2)mu?

Therefore kinetic energy is greater for the outer car.

25.2)

K = (1/2)IW

As moment of inertia (I) is greater for the hoop, therefore, the flywheel(hoop) will have more kinetic energy.

(For hoop,
I = mR
. For disc ,
I = mR/2
)