Moments Flashcards
(14 cards)
what is the equation for momentum?
momentum = mass x velocity
What are the units of momentum?
kg m/s
What happens to momentum when no external forces act on it?
Momentum is conserved:
momentum before = momentum after
what is the equation linking force and momentum?
force = change in momentum / time(s)
How are cars adapted to increase the time taken for momentum to change?
crumple zones - increases time taken for car to stop
Seat belts - reduces force acting on the chest as it increases the time taken for the wearer to stop.
Air bags - slow you down more gradually
Why is it important that cars take as long as possible for a change in momentum?
The longer the time taken for a change in momentum, the smaller the force is, so crashes are (probably) less severe.
What is a moment?
The turning effect of a force
what is the equation linking moments and forces?
moment = force x perp. distance
What is the centre of gravity?
The point through which the weight of a body acts.
Where does the centre of gravity hang?
directly below the point of suspension
How to find the centre of gravity of a flat object?
1) suspend the shape and a plumb line from the same point and wait until they stop moving.
2)Draw a line along the plumb line
3)Suspend the shape and line from a different pivot point and do repeat
4) centre of gravity is where the two lines cross.
What is another way to find the centre of gravity of a flat object?
Find where the lines of symmetry meet
What is the equation which shows that moments are balanced?
total anticlockwise moments = total clockwise moments
What happens if the moments are not equal?
There will be a resultant force, therefore the object will turn.
