Question

A bus travelling the first one third distance at a speed of 10 km/h, the next one third at 20 km/h and the last one-third at 60 km/h. The average speed of the bus is
(a) 9 km/h (b) 16 km/h (c) 18 km/h (d) 48 km/h 6. A car moves a distance of 200 m. It covers

Answer 1

Acceleration = Change in velocity / Time

                     = v - u / t

72km/h = 72 × 5 / 18 m/s = 20m/s

54km/h = 54 × 5 / 18m/s  = 15m/s

     Acceleration = 20-15 / 10 

                           = 5 /10 

                           = 0.5 m/s²

To find distance we use the formula 

              v² = u² + 2aS   here v is the final velocitiy (72km/h)

                                              u is the initial velocity(54km/h)

                                               a is the acceleration

                                              S is the distance

             20² = 15² + 2 × 0.5 × S 

             400 = 225 + 1×S

             400 - 225 = S

           S = 175 m

Therefore distance = 175m