A wheel with 50 cm diameter is moving at a speed of 20 m/sec. (a) How fast is the wheel turning? (b) How many revolutions will the wheel turn if it coasts uniformly to rest in 30 sec?

Answer 1

C=pi*D = 3.14 * 50 = 157.1cm. = 1.57m

a. Va=(20m/s / 1.57m)rev *6.28rad/rev =
80rad/s. = Angular velocity.

b. a = (Vf - Vo) / t,
a = (0 - 80) / 30 = -2.666rad/s^2.

b. d = Vo*t + 0.5a*t^2,
d = 80*30 - 1.333*(30)^2 = 1200.rad.

Rev = 1200rad / 6.28rad/rev = 191.