Question

A car is traveling at a steady 79 km/h in a 50 km/h zone. a police motorcycle takes off at the instant the car passes it, accelerating at a steady 7.9 m/s2 .how much time elapses before the motorcycle is moving as fast as the car?

Answer 1

We use the kinematic equation,to determine the time required for the motorcycle to reach the car's speed.

`v=u+at`

Here, v is the velocity of motorcycle after time t, and u is the initial velocity and police motorcycle moves with acceleration a.

Given
`v=79 km/h=(79*10^3 m)/(60*60s) =21.9 m/s` and
`a=7.9 m/s^2` . Take
`u=0`.

Substituting these values in above equation we get,

`21.9 m/s=0+7.9 m/s^2* t\\\\t =(21.9m/s)/(7.9 m/s^2) =2.77 s`

Thus, the motorcycle is moving as fast as the car after 2.77 s.