a car of mass 500kg is moving at 24m/s. A lion of mass 100kg drops on to the roof of the car from an overhanging branch. Show that the car will slow down to 20m/s.
Given
M1=500kg
U1=24m/s
M2=100kg
U2=0
V=20?
Req
V=?
Soln
M1u1+m2u2=v(m1+m2)
500kg*24m/s + 100kg*0=v(500kg + 100kg)
12000kgm/s + 0=v(600kg)
12000kgm/s=v(600kg)
12000kgm/600kg=v(600kg)/600kg
So v=20m/s
momentum before = 24 *500 = 12,000
so momentum after = 12,000
v * 600 = 12,000
v = 20
Good
at first momentum is conserved. This means momentum before collision and momentum after collision are equal.
momentum before collision = initial momentum of a lion + initial momentum of a car
initial momentum of a lion is zero because as it drops from overhanging branch its initial velocity will be zero
initial momentum of a car = mass of car * initial velocity of car = 500 kg * 24 m/s
momentum before collision = 0 + 1200 kg m/s
momentum after collis