Brainlag PlusWhen things start at rest and fly apart, the total momentum stays zero, so the pieces move off with equal and opposite momentum.
Zero before, zero after
Before a cannon fires, nothing moves: the total momentum is zero.
Momentum is conserved, so just after firing the total is still zero. The ball goes forwards with some momentum; the cannon must go backwards with the same amount.
0 = m₁v₁ + m₂v₂
so m₁v₁ = m₂v₂ in size, in opposite directions
The heavy cannon recoils slowly; the light ball flies off fast. Their momenta are the same size.
The rest of this lesson and its 9 practice questions are in Plus.
Screen 1 of 4, free to read.
- 9 exam-style questions, marked as you go, each with a worked solution
- Anything you get wrong is saved to your flashcards