Conservation of Momentum Flashcards
All 4 cards in this deck
State the law of conservation of momentum.
The total momentum before a collision equals the total momentum after the collision, provided no external forces act.
What are the steps to explain, using Newton's third law, why momentum is conserved in a collision?
e.g. two trolleys colliding- The force of each trolley on the other is equal and opposite.
- The time of the collision is the same for both, so the changes in momentum are equal and opposite.
- So there is no overall change in momentum: momentum before = momentum after.
Two objects at rest are pushed apart in an explosion (e.g. a gun firing a bullet). What is their total momentum afterwards?
Zero — the two momenta are equal in size and opposite in direction, because the total momentum before was zero.
True or false? In a collision, momentum is conserved but kinetic energy need not be.
True. Kinetic energy can be transferred to thermal and sound stores while the total momentum stays the same.