Question

A cart of mass 50 kg moving at a speed of 20 km/h hits a lighter cart B of mass 20kg moving towards it at a speed of 10 km/h.The two carts cling to each other.Find speed of the combined mass after the collision.

• A. $\frac{10}{7}Km/h$
• B. $\frac{78}{7}Km/h$
• C. $\frac{80}{7}Km/h$
• D. $\frac{82}{8}Km/h$

Answer 1

The correct option is C $\frac{80}{7}Km/h$

Given,

Velocity of cart $A$ having mass $50kg$ is $20km/h$

Velocity of cart $B$ having mass $20kg$ is $10km/h$

Mass after collision is $50+20=70kg$

Now

Momentum is conserved before and after collision therefore, we can write equation as,

$50\times 20-20\times 10=70\times V1000-200=70VV=\frac{800}{70}V=\frac{80}{7}km/h$

Hence, velocity after collision is $80/7km/h$

correct option is $\left(C\right)$