Question

A motorcyclist riding motorcycle A is travelling at a speed of 20 m/s applies the brakes and stops the motorcycle in 10 s . Another motorcyclist B whois travelling at a speed of 5 m/s applies the brakes and stops the motorcycle in 20 s . Plot speed - time graph for the two motorcycles . Which of the two motorcycles travelled further before it comes to a stop ? A cyclist goes around a circular track once every 2 minutes . If radius of the circular track is 110 m , calculate the speed ofcyclist ?

Answer 1

deceleration = a1 = (0- 20 m/s)  / 10 s  = - 2 m/sec^2
distance traveled by the first one :  s = ut + 1/2 a t^2
    = 20 * 10 - 1/2 * 2 * 10^2 = 100 m

deceleration = a2 = -5/20 = -1/4 m/s^2
distance traveled by the 2nd motorist: 
    = 5 * 20 - 1/2 * 1/4 * 20^2 = 50 m

The first motorist traveled more.
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Cyclist

speed = circumference / time duration = 2 * 22/7 * 110 /120 sec
           = 121/21  m/s