Two objects of masses 100 g and 200 g are moving along the same line and direction with velocities of 2 m s-1 and 1 m s-1, respectively. They collide and after the collision, the first object moves at a velocity of 1.67 m s-1. Determine the velocity of the second object.
Mass of one of the objects, m1 = 100 g = 100/1000 = 0.1 kg
Mass of the other object, m2 = 200 g = 200/1000 = 0.2 kg
Velocity of m1 before collision, v1 = 2 m/s
Velocity of m2 before collision, v2 = 1 m/s
Velocity of m1 after collision, v3 = 1.67 m/s
Velocity of m2 after collision = v4 = ?
By law of conservation of momentum :
Total momentum before collision = Total momentum after collision
m1v1 + m2v2 = m1v3 + m2v4
(0.1)2 + (0.2)1 = (0.1)1.67 + (0.2)v4
0.4 = 0.167 + 0.2v4
v4 = 1.165 m/s
The velocity of the second object after collision 1.165 m/s.
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Akhtar, Kiran and Rahul were riding in a motorcar that was moving with a high velocity on an expressway when an insect hit the windshield and got stuck on the windscreen. Akhtar and Kiran started pondering over the situation. Kiran suggested that the insect suffered a greater change in momentum as compared to the change in momentum of the motorcar (because the change in the velocity of the insect was much more than that of the motorcar). Akhtar said that since the motorcar was moving with a larger velocity, it exerted a larger force on the insect. And as a result the insect died. Rahul while putting an entirely new explanation said that both the motorcar and the insect experienced the same force and a change in their momentum. Comment on these suggestions
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Fig. 8.11
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