Question

An object of mass 1 kg travelling in a straight line with a velocity​ of 10 m/s collides with, and sticks to, a stationary wooden​ block of mass 5 kg. Then they both move off together in the​ same straight line. Calculate the total momentum just before​ the impact and just after the impact. Also, calculate the velocity​ of the combined object.

Answer 1

Given: $m=1kg$, $u_1=10m/s$,
$M=5kg$, $u_2=0m/s$. ​

Solution​

From conservation of momentum​

Initial momentum = Final momentum​

$m\times u_1+M\times u_2=(m+M)\times v$

$1\times 10+5\times 0=(1+5)\times v$

$10=6v$

Hence, the velocity of combined object is $v=\frac{5}{3}m/s$

Total momentum before is $10kgm/s$​

From momentum conservation, total momentum after is $10kgm/s$.