Momentum and Force

Question 0

When two objects push each other apart they move…. (2points)??

Answer 0

• with different speeds if they have unequal masses

* with equal and opposite momentum, so their total momentum is zero (eg A = +30N; B=-30N)

Question 1

Momentum equation?
Unit of momentum?
When is it conserved( law of the conservation of momentum)?

For 2 trolleys of the same mass…
For a single trolley pushed into a double trolley….

Answer 1

Momentum= mass x velocity
Unit= kg m/s
Momentum is conserved whenever objects interact providing that they’re in a closed system so that no external forces act on them

Question 2

When vehicles collide the force of the impact depends on….

The longer the impact time…

When two vehicles collide….

Answer 2

Force of impact depends on mass, change of velocity and duration of impact

Longer impact time, more impact force is reduced

Collision= exert equal and opposite forces on each other + their momentum is unchanged

Question 3

Impact time

Force = change of momentum/ time

Answer 3

Crumple zones can reduce impact force as they increase impact time (at rear and front of all cars)
So do side impact zones

Question 4

SAFETY!!!

Seatbelts
Air bags
Crumple zones
Child car seats

Answer 4

Seatbelts and air bags spread the force across the chest and increase the impact time.
• a seatbelt stops it’s wearer from continuing forwards when the car stops suddenly(force on the chest not on head when going through windscreen)

Question 5

Conservation of momentum can be used to find the speed of a car before an impact

Answer 5

Momentum = mass x velocity change
—————————–
Time