Question

Freya has a mass of 14kg she is running at 1.1m/s to the left when she runs into Eric, who is standing still. Eric has a mass of 18kg. After the collision, they continue moving together. What is their velocity after the collision.
A. 0.48 m/s to the left
B. 2.5 m/s to the left
C. 0.86 m/s to the left
D. 1.4 m/s to the left

Answer 1

Their final velocity  is 0.48 m/s.

We can use conservation of momentum to calculate the magnitude of the final velocity.

Momentum before collision is equal to the momentum after collision

m1v1+m2v2=(m1+m2)v

here, v is final velocity , assuming right side velocity as positive, and left side velocity as negative.

14*(-1.1)+18*(0)=(14+18)v

v=-0.48 m/s

Here, negative sign indicates that they both  will move in left direction.