Question

a biker starts a race and crosses the half line in 3 second with speed 54km/h and after that he increases his speed uniformally at a rate 7.5m/s² and completed the race in 5 second.choose the correct option - 1.Acceleration in the first half is 5 m/s².2.He finished the rae with speed 108km/h.3acceleration in the second half of the race is 12.5m/s².NOTE MORE THAN ONE OPTION CAN BE CORRECT​

Answer 1

Answer:

54 km/hr is 15m/s

distance traveled = speed × time =15×3 = 45m

Explanation:

speed in second half = 15+7.5 = 22.5m/s

time = 5s

distance = 22.5×5 = 112.5m

1. acceleration first half = speed/time = 15/3 =5m/s square

2. speed = distance ÷ time = (45 + 112.5) ÷ (3+5) = 157.5/8

= 19.68 m/s = 70.84 km/h

3. acceleration 2nd half = 22.5/5 = 4.5 m/s square

option 1 is only correct

to convert km/h to m/s multiply by 5/18

to convert m/s into km/h multiply by 18/5