Question

A car is moving with velocity 20 m/s and after 1/2 hour velocity is 54 km/h what is average velocity?

Answer 1

Assumption is that it starts with Vel. of 20m/ s moves with accln.for 1/2 an hour and achieve a Vel. of 54km/hour. With this assumption we can find displacement.

54km./ h= 54×5/18 m/s= 15m/s

In fact a retardation is working.

So

15 = 20-a1800

5= a1800

a= 5/1800(retardation)

S= 20×1800–1/2*5/1800* 1800^2

S= 36000–900*5

S= 36000–4500

S= 31500meter

Average Vel.= 31500/1800= 315/18m/s

Average Vel. 17.5m/s.= 17.5×18/5km/h= 3.5×18km/h= 63km/HR.

Hope this will help you.... ✌