Question

An object of mass 2 kg is moving with a velocity of 3 m/s and collide head-on with an object B of mass 1 kg moving in the opposite direction with a velocity of 4 m/s. after the collision, both objects coalesce so that they move with a common velocity v equal to

• A. $\frac{2}{3}m/s$
• B. 1 m/s
• C. 2 m/s
• D. 3 m/s

Answer 1

The correct option is A $\frac{2}{3}m/s$

Net momentum before collision is $2kg\times 3m/s+(-1kg\times 4m/s)=2Kgm/s$, $negative$ sign because in $opposite$ direction.

After the collision the get stuck to each other so the mass becomes $1+2=3kg$

if the new velocity is $v$ then the new momentum should be equal to the old one, so $3v=2$ or $v=\frac{2}{3}m/s$ in the

direction of $original$ direction of $2kg$