Forces Flashcards

State the SI unit for momentum.

kg m/s

Compare the momentum of two cars of the same mass but one travelling faster than the other.

The car travelling faster has more momentum.

Name the pathways by which energy can be transferred.

Mechanically, electrically, by waves or by radiation.

Law of Conservation of Momentum

In a closed system, the total momentum before an event is equal to the total momentum after an event.

collisions meaning

A collision is when two objects come together and interact, and momentum is conserved.

explosion meaning

An explosion is when one object splits into parts that move apart, and momentum is conserved.

How to solve collision questions

• Choose a positive direction (usually right).

• Calculate momentum of each object before.

• Add them to get total momentum before.

• Set equal to total momentum after.

• Solve for unknown velocity/mass.

EXPLOSIONS momentum rule

Before an explosion, total momentum = 0 (because everything is stationary). Afterwards, momentum is still 0, so the pieces move with equal and opposite momentum.

They would have the same momentum but in opposite directions before the collision, so momentum before = 0.

Total momentum after = 0, so if they have the same mass, they will have the same speeds in opposite directions.

Total momentum before would be towards the right.

Total momentum after would also be towards the right.

So, they may both move off together towards the right or trolley 1 would rebound more slowly than trolley 2.

Momentum before = 0.

Total momentum after = 0, so if they have the same mass, they will have the same speeds in opposite directions.