Get premium membership and access revision papers with marking schemes, video lessons and live classes.
OR

Form 3 Physics Newton's laws of motion questions and answers

A minibus of mass 1,500 kg travelling at a constant velocity of 72 km/h collides head-on with a stationary car of
mass 900 kg. The impact takes 2 seconds before the two move together at a constant velocity for 20 seconds.
Calculate
a).The common velocity
b).The distance moved after the impact
c).The impulsive force
d).The change in kinetic energy

(9m 29s)
1330 Views     SHARE

a).Let the common velocity be ‘v’ Momentum before collision = momentum after collision
(1500times20) + (900times0) = (1500 +900) v
30000 = 2400v
v = 30000/2400 = 12.5 m/s (common velocity)
b).After impact, the two bodies move together as one with a velocity of 12.5 m/s
Distance = velocity times time
= 12.5 times 20
= 250m
c).Impulse = change in momentum
= 1500 (20-12.5) for minibus or
=900 (12.5 – 0) for the car
= 11250 Ns
Impulse force F =(impu lse)/(time) =
11250/2 = 5,625 N
d).K.E before collision
= ½ times 1,500 times 20^2 = 3 times 10^5 J
K.E after collision = ½ times 2400 times 12.52 = 1.875times 10^5 J
Therefore, change in
K.E = (3.00 – 1.875) times 10^5 = 1.25times 10^5 J

|