P7

Question 1

Newtons laws

Answer 1

1st - Object remains at rest or with constant velocity unless acted on by resultant force
2nd - force required to move an object proportional to mass and acceleration
3rd - Two interacting objects will exert forces of equal magnitudes but in opposite directions

Question 2

collision types

Answer 2

elastic - momentum, ke, total energy conserved
inelastic - momentum total energy conserved but not ke - probably heat

Question 3

momentum + conservation

Answer 3

p = mv
vector value
total momentum before = total momentum after a collision in a closed system (no other forces)

Question 4

Air bags

Answer 4

deform and expand to cushion - more time interaction = less rate of change of p = less force = less damage

Question 5

Angled collisions

Answer 5

resolve the components and equate change of momentum to 0
e.g when balls collide they always move 90 degrees to each other

Question 6

2nd law

Answer 6

net force proportional to rate of change of momentum (in same direction)
F = change of momentum/ time
as k = 1 in f = kp

Question 7

linking f = ma to momentum

Answer 7

f = mv - mu/t = m (v-u/t) = ma

Question 8

why is momentum conserved

Answer 8

two object interaction - equal but opposite force
net force = 0 so change in p/t = 0 so change in p = 0 - conserved

Question 9

Impulse

Answer 9

impulse = change in momentum
kim’s-1 or Ns
= force x time
area under a force time graph