Acar moving at 10.0 m/s crashes into a barrier and stops in 0.050 s. there is a 20.0-kg child in the car. assume that the child’s velocity is changed by the same amount as that of the car, and in the same time period. what is the impulse needed to stop the child?

The impulse needed to stop the child = -200 Ns

Explanation:

Impulse: This can be defined as the product of force and time of a body. The S.I unit of impulse is kgm/s or Ns

From newton's second law,

I = mΔv Equation 1.

Where I = Impulse needed to stop the child, m = mass of the child, Δ = change in velocity of the child.

Given: m = 20.0 kg,

Δv = v-u where v =0 m/s, u = 10.0 m/s

Δv = 0-10 = -10 m/s.

Substituting into equation 1

I = 20(-10)

I = -200 Ns.

Thus the impulse needed to stop the child = -200 Ns

Note: The negative sign shows that the impulse act against the motion of the child

when jerome paddle in flowing river towards east the net speed of jerome will increase

so the net speed of jerome will be given as

now the speed of paul will be same as it is given as he is running on the ground

so

so here we can say since the speed of jerome is more so he will win the race

now as we know the distance so the time difference is given as

so jerome will reach first and the time difference will be 203.55 s or 3.4 min