What is the velocity

Question

a 1.5 kg ball is moving at 8 m/s south, strikes a 2 kg ball moving at 3 m/s south. if the velocity of the 2 kg ball after the collision is 4.5 m/s south, what is the velocity of the 1.5 kg ball

Answer 1

Hi Meg K.,

Due to conservation of momentum, and both balls moving south, you can use the equation m₁v₁ + m₂v₂ = m₁v'₁ + m₂v'₂, where:

m₁ = 1.5 kg

m₂ = 2 kg

v₁ = 8 m/s

v₂ = 3 m/s

v'₂ = 4.5 m/s

Then solve for v'₁.

v'₁ = (m₁v₁ + m₂v₂ - m₂v'₂)/m₁, (plug and chug).

Your answer will be, ___ m/s south, (velocity has both magnitude and direction).

I hope this helps, Joe.

Answer 2

Applying the law of conservation of momentum which states that "the total momentum of a system before collision is equal to the total momentum after collision".

Assuming that South is positive,

1.5•8 + 2•3 = 1.5•v +2•4.5

Solving for v 12+6-9=1.5•v

i.e. 9/1.5=v

∴ v = 6 ms^-1 Since this value is positive, the resultant direction is South.

If you have any further questions about this or any other problem, feel free to ask Mr. Frank A

Answer 3

By law of Conservation of momentum : m₁V₁ + m₂V₂ = m₁V₁' + m₂V₂';

From here V₁' = (m₁V₁ + m₂V₂ - m₂V₂')/m_{1 = (1.5kg·8m/s + 2kg·3m/s - 2kg·4.5m/s)/1.5kg = 6m/s also south}