Question

Assertion: If two bodies of equal masses undergo elastic collision in one dimension, then
after the collision the bodies will exchange their velocities.
Reason: In elastic collision, velocity of approach is equal and opposite of velocity of
separation.
(1)​

Answer 1

Answer:

You will observe that leaves do not turn blue-black in colour. This is because of utilisation of starch stored in the leaves and lack of photosynthesis in the absence of sunlight. Select a healthy green leaf of a potted plant.

Answer 2

Answer:

Both assertion and reason are correct.

Explanation:

Given: Two bodies of equal masses = $m$(say).

Let A and B move with initial velocities $u_1$ and $u_2$ respectively and final velocities $v_1$ and $v_2$ respectively.

Now, From conservation of linear momentum:

$mu_1+mu_2= mv_1+mv_2\\\implies u_1+u_2= v_1+v_2----(1)$

$\implies u_1-v_1=v_2-u_2----(2)$

From conservation of energy:

$\frac{1}{2}mu_1^2+\frac{1}{2}mu_2^2=\frac{1}{2}mv_1^2+\frac{1}{2}mv_1^2$

$\implies u_1^2+u_2^2=v_1^2+v_1^2----(3)$

$\implies u_1^2-v_1^2=v_2^2-u_2^2----(4)$

$(4)/(3) \implies \frac{u_1^2-v_1^2}{u_1-v_1} = \frac{v_2^2-u_2^2}{v_2+u_2}$

$\implies u_1+v_1= v_2+u_2\\\implies u_1-u_2= v_2+v_1----(5)$

velocity of approach = velocity of separation.

Therefore, reason is correct.

$(1)+(5) \implies 2u_1= 2v_2\\(1)-(5) \implies 2u_2= 2v_1$

Therefore, assertion is also correct.