1.

A bus starts from rest with constant acceleration of 5 m/s×s.At the same time a car travelling with a constant velocity 50m/s over takes tales and passes the bus.How fast isbthe bis travelling when they are side by side?

Answer»

Let after time t the bus will over the car.

let s be the distance travelled by the bus to overtake the car.

For bus : As a = 5 m/s^2 ; u = 0 m/s

so, s = u t + 1/2 a t^2

or, s = 0 + 1/2 ×5 × t^2

so, s = 5/2 t^2

Also, the distance travelled by the car in the same time t with v = 50 m/s

d = v t = 50 × t

As both s and d is the same distance

so, s = d

or, 5/2 t^2 = 50 t

or, t^2 - 20 t = 0

or, t ( t - 20 ) = 0

so, t = 20 s ; { 0 s NEGLECTED }

As v = u + a t

so, velocity of bus after 20 s

v = 0 + 5 × 20 = 100 m/s

the bus will be TRAVELLING then at a speed of

100 m/s.


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