Question 103: Centre of Mass and Rotational Motion

Question

Two bodies A and B of masses 5 kg and 8 kg are moving such that the momentum of body B is twice that of the body A. The ratio of their kinetic energies will be :

Accepted Answer

Given,
Mass of body A = 5 kg
Mass of body B = 8 kg
Momentum of body B is twice that of body A,
$$	herefore$$ $${P_B} = 2{P_A}$$
We know,
Kinetic Energy $$(K) = {{{P^2}} \over {2m}}$$
$$	herefore$$ $${{{K_A}} \over {{K_B}}} = {\left( {{{{P_A}} \over {{P_B}}}} ight)^2} 	imes {{{m_B}} \over {{m_A}}}$$
$$ = {\left( {{1 \over 2}} ight)^2} 	imes {8 \over 5}$$
$$ = {1 \over 4} 	imes {8 \over 5}$$
$$ = {2 \over 5}$$

Answer

4 : 5

Answer

2 : 5

Answer

5 : 4

Answer

5 : 2

Centre of Mass and Rotational Motion

Two bodies A and B of masses 5 kg and 8 kg are moving such that the momentum of body B is twice that of the body A. The ratio of their kinetic energies will be :

Choose the correct answer: