Question

on a level road, a scooterist applies brakes to slow down from a speed of 10 m/s to 5m/s. if the mass of the scooterist and the scooter be 150 kg, calculate the work done by the brakes.( neglect air resistance and friction)

Answer 1

Work done = Change in Kinetic energy

= 0.5mv² - 0.5mu²

= 0.5m (v² - u²)

= 0.5 × 150 kg × [(5 m/s)² - (10 m/s)²]

= -5625 J

= -5.625 kJ

Work done by brakes is -5.625 kJ

Here negative sign indicates that work is done against the motion of scooter.

Answer 2

Answer:

Explanation:

Solution :-

Given :-

Total Mass, m = 86 + 64 = 150 kg

Initial speed, u = 36 kg/h

= 36 × 1000/3600 = 10 m/s

Final speed, v = 18 × 1000/3600 = 5 m/s

To Calculate :-

Work Done, W = ??

Formula to be used :-

W = 1/2mv² - 1/2mu²

W = 1/2 × 150 × 5² - 1/2 × 150 × 10²

W = - 5625 J

Negative sign indicates that the work is done on the scooter.