Question

A car moving at a speed of 30 km/h is brought to rest in 8 m by applying break. If the same car is travelling at 60 km/h, it can be brought to halt with the same breaking force in ___________.

A particle is moving in a straiht line with initial velocity U and uniform acceleration 'a''. if the sum of the distance travelled in t and t+1 seconds is 00cm.then its velocity after t second is?
How?

Answer 1

Initial velocity u = 30 km/h
Final velocity v = 0 km/h
Acceleration a = (v2 − u2)/(2S)
                          = (0 − 900)(1000/3600)2/(2x8)
                          = − 900x5x5/(18x18x2x8) m/s2  
                          =  − 4.34 m/s2.
Same breaking force means same acceleration. Now we have to calculate S for u = 60 km/h.
S = (v2 − u2)/(2a)
    = − 3600 x 5x5/(18x18x2x(−4.34)) m/s2 
    = 800.05 m