Question

A hammer of weight $2\text{kg}$, moving with velocity $8\text{m/s}$, strikes against the head of a spike, and drives it into a block of wood. If hammer comes to rest in $0.02\text{sec}$, the impule associated with the spike will be:

• A. $30\text{Ns}$
• B. $-16\text{Ns}$
• C. $-30\text{Ns}$
• D. $16\text{Ns}$

Answer 1

The correct option is D $16\text{Ns}$

Initial momentum of the hammer $P_i=mu=2\times 8=16\text{kg m/s}$
Final momentum of the hammer $P_f=0$
Change in momentum of the hammer $\Delta P=P_f-P_i$
$\Delta P=0-16\Delta P=-16\text{kg m/s}$
Impulse acting on the hammer
$I_{hammer}=\Delta P=-16\text{Ns}$
Impulse acting on the spike
$I_{spike}=-I_{hammer}=16\text{Ns}$