Question

A 4-kilogram mass has a speed of 6 meters per second on a horizontal frictionless surface, as shown above. The mass collided head-on and elastically with an identical 4-kilogram mass initially at rest. The second 4-kilogram mass then collided head-on and sticks to a third 4-kilogram mass initially at rest. The final speed of the first 4-kilogram mass is:

A) 12 m/s
B) 6 m/s
C) 3 m/s
D) 0 m/s

Answer 1

In an elastic collision, the final speed of the first 4-kilogram mass is 6 m/s, which is the initial speed of the system.

Step-by-step explanation:

In an elastic collision, both momentum and kinetic energy are conserved. So, in this head-on elastic collision, the first 4-kilogram mass will transfer some of its momentum and kinetic energy to the second 4-kilogram mass, causing it to move. Since the collision is head-on and elastic, the second 4-kilogram mass will then transfer its momentum and kinetic energy to the third 4-kilogram mass, causing it to move as well.

Since the total mass of the system remains the same and the collision is elastic, the final speed of the first 4-kilogram mass will be 6 m/s, which is the initial speed of the system.