A ball with a mass of 3 kg moving at 5 m/s collides with a 9 kg ball at rest. After the collision, the impacting (3 kg) ball bounces back at a speed of 2.5 m/s. How fast does the 9 kg ball move and in what direction

The second ball moves with 0.83 m/s forward.

Explanation:

Given;

mass of the first ball, m₁ = 3 kg

initial velocity of the first ball, u₁ = 5 m/s

final velocity of the first ball, v₁ = 2.5 m/s

mass of the second ball, m₂ = 9kg

initial velocity of the second ball, u₂ = 0

final velocity of the second ball, v₂ = ?

From the principle of conservation of linear momentum;

m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂

(3x5) + (9x0) = (3x2.5) + (9v₂)

15 = 7.5 + 9v₂

15 - 7.5 = 9v₂

9v₂ = 7.5

v₂ = 7.5/9

v₂ = 0.83 m/s

The second ball moves with 0.83 m/s forward.

ill do it for 100, also this isnt 80 its 40

force required to detach it is given by

charges are taken to be fundamental charge

now we have

so above is the minimum distance at which it will detach