Question

9. How much force is required to stop a bus (in 10 seconds) of mass 5000 kg moving with a
speed of 72 km/h?
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Answer 1

Force = mass × acceleration

There is retardation here.

initial velocity =72km/h=20m/s

final velocity =0 m/s

retardation =0-20/10

=-20/10

=-2m/s²

Force = 5000×-2

= -1000kgm/s²

=-1000N

Answer 2

Answer:

-10000 N

Explanation:

Mass of bus = 5000 kg

Acceleration = v - u/t

u = 72 * 5/18 m/s

= 20 m/s

= 0 - 20/10

= -20/10 = -2 m/$s^{2}$

F = Mass * Acceleration

= 5000 * -2

= -10000 N