A 8 kg ball is moving with a speed of 10 m/s directly toward a 4 kg ball which is at rest. The two balls collide and stick together. What is their
velocity immediately after the collision?

v₃ = 6.67 [m/s]

Explanation:

To solve this problem we must use the linear momentum conservation theorem, which tells us that momentum is preserved before and after the collision.

Let's take the ball movement of 8 [kg] as positive.

Therefore we can built the following equation:

where:

m₁ = mass of the 8 [kg] ball

m₂ = mass of the 4 [kg ] ball

v₁ = velocity of the 8 [kg} ball before the colllision = 10 [m/s]

v₂ = velocity of the 4 [kg] ball before the colllision = 0 [m/s] (at rest)

v₃ = velocity of the two balls after the collision [m/s]

less than one you can't create energy

float.

archimedes' principle

denser than water sinks in water.

denser than mercury would sink in it