Q6 of 35 Page 143

A scooter of mass 120kg is moving with a uniform velocity of 108km/hr. Find out the force required to stop the vehicle in 10s?


First, as the, all the units are not same there's a need of conversion:-


108 km/hr into m/s


We know that,


1 km has 1000 m, and 1hour has 3600s.


Then, = 30m/s = u


According to Second law of motion,


Force = Change in momentum/time


=


=


=


= –360N


OR


Using First Equation of motion


v = u + at


0 = 30m/s + a (10s)


–30m/s = (10s) a


–3m/s2 = a


As,


Force = mass × acceleration


= 120kg × (–3m/s2)


= –360N


NOTE: Negative sign shows that force and acceleration produced are opposite to that of motion.


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