Question

a) Derive first law of Newton from second law.
(b). Find the force required to stop a car of mass 100 kg with two passengers each of 50 kg sitting inside, if it is moving at 60 km/hr speed and takes 5 s to stop.​

Answer 1

Answer:

first law state that if a body is at rest and move with constant velocity unit a net force applied to it. Newton 2 law state that the net force applied on the body is equal to rate of change in momentum.

F=ma

F=m(v-u)/t

Ft=mv-mu.

b) mass of car 100kg

two passenger each of 50 kg

initial vel is 60 km/ h= 60*5/18=50/3

var takes 5 s

intial vel u= 50/3

final vel v=0

v=u+at

a=v-u/t=0-50/3/5=10/3m/s

total mass= mass of car + mass of two passenger

=100+2(50)= 100+100=200kg

f=ma

=200*10/3

=2000/3

=666.6N