Question

A rubber of mass $200$ g hits a wall normally with a velocity of ${10ms}^{-1}$ and bounces back with a velocity of ${8ms}^{-1}$. The impulse is _____ Ns.

• A. $-0.5$
• B. $+0.5$
• C. $-3.6$
• D. $+3.6$

Answer 1

The correct option is C $-3.6$

Initial momentum $P_i=mu=0.2\times \left(10\right)=2kgm/s$

Final impulse $P_f=mv=0.2\times (-8)=-1.6kgm/s$

Impulse $I=P_f-P_i$

$⟹I=-1.6-2=-3.6Ns$