Answer:
Option A
20 m/s
Explanation:
From the law of conservation of linear momentum, the sum of momentum before and after collision equals zero hence for this case also, the sum of momentum of the two cars before collision should be equal to momentum after collision.
Momentum is given as the product of mass and velocity, where velocity considers the direction. Momentum, p=mv where m is the mass of the object and v is the velocity.
Momentum before collision
Since the velocities of both cars before collision are zero hence their momentum are zero ie 0.5*0+(1*0)=0
Momentum after collision
For 0.5 Kg car, its momentum will be 0.5*-40=-20 Kg.m/s
For the 1 kg car its momentum will be 1*v=1v
v-20=0
v=20 m/s
