Question 39:
(a) State the law of conservation of momentum.
(b) Discuss the conservation of momentum in each of the following cases :
(i) a rocket taking off from ground.
(ii) flying of a jet aeroplane.
Lakhmir Singh Physics Class 9
Answers
Answer:
(a) the law of conservation of momentum states that in the absence of net external force on the system, the momentum of the system remains unchanged m1u1+m2u2=m1v1 +m2v2
(b)
Explanation:
a) The law on the conservation of momentum states that the total momentum before and after the collision is equal for two objects colliding in an isolated system
b) i. Before launching, a rocket's total momentum and fuel is zero. During the launch, the downward momentum of the expanding exhaust gasses is equal to the upward momentum of the rising rocket in magnitude, so that the system's total momentum remains constant at zero value. In a two-particle collision, the sum of the two momentum before collision is equal to the sum after collision.
ii. The turbine operates the compressor in the aircraft and drives the gas at a higher speed through the tail piece of engine. This leads to the forward momentum and the jet moves forward. The forward momentum is equal to the gas reverse momentum. The burning and ejection rates of gases in the fuel burning chamber are adapted to achieve the required momentum rise in the forward direction.