Additional Forces and motion for separate science

Question 1

Explain which source of error may prevent you from proving the law of conservation of momentum in the trolley explosion experiment.

Answer 1

There is friction in the axles of the wheels of the trolleys, if this effects each trolley by a different amount then it will appear that the sum of the momentums does not equal zero, as more momentum in one direction is lost than in the other dierction

Question 2

State newtons third law

How does this law means that momentum must be conserged in any collision.

Answer 2

Newtons third law states that if body A exerts a force on body B, then body B will exert a force back on body A of equal magnitude but opposite direction.

As in any collision there is two equal forces, each one will cause exactly the same change of momentum. However the changes of momentum are in oppsite directions. This means that one of them is positive and the other is negative, and as they have the same size they cancel each other out. This leaves the total momentum the same as the original momentum.

Question 3

What is the formula that relates force and change of momentum.

Example calculation: in a collision the momentum of a body changes from 5kgm/s to 20kgm/s. If the force was acting for half a second, how large was the force tha caused this change?

Answer 3

Momentum and force are related by this equation:

Force x time = change of momentum

The quantity ‘force x time’ is also known as impulse

Example calculations:

force = change of momentum/time

= 15/0.5

= 30N

Question 4

Explain how car safety features can reduce the size of the force experinced by a driver if they have a crash.

Give some examples.

Answer 4

Car safety features work by increasing the time it takes for the person to stop. As this means that there is the same change of momentum but over a longer time, the size of the force is lower.

Examples:

Crumple zone: the bonet wil crumple up, acting as a cusion which increases the time taken for the driver to stop

Air bag: this is an air filled cushion that slowly compresses under force. This slow compressin increases the time it takes to stop