Question

How long will it take a force of 10 N to stop a mass of 2.5 kg which is moving at 20 m/s?

Answer 1

Here F=10N
m=2.5 kg


so, a= f/m
a=10/2.5
a=4m/sec^2


Now, a=v-u/t
a=4m/s^2
v=0
u=20 m/s

so, 4= 0-20/t
4= -20/t


so, t= -4/20
t= 0.2 sec (as time cannot be negative)