How do i do this?

Question

In an isolated system, two roller skaters, each with a mass of 100 kg, collide. Skater 1 was initially at rest, while Skater 2 was moving at 6 m/s. They move off together. What is their speed?

A. 3 m/s
B. 6 m/s
C. 10 m/s
D. 0 m/s

Answer 1

In an isolated system, two roller skaters, each with a mass of 100 kg, collide. Skater 1 was initially at rest, while Skater 2 was moving at 6 m/s. They move off together. What is their speed?

 

 

Let m=100kg

     v=6m/s

     V=?

 

Use the momentum conservation law:

net momentum before collision = net momentum after the collision

or  m*v=2m*V

 

So,  V=m*v/(2m)= v/2 = 6m/s*(1/2)=3m/s

 

The answer is A. 3m/s