Question

8. If a ball is thrown upwards from the surface of earth:
(A) The earth remains stationary while the ball moves upwards (B) The ball remains stationary while the earth
moves downwards (C) The ball and earth both moves towards each other (D) The ball and earth both move
away from each other
9. Fast neutrons can easily be slow down by
(A) The use of lead shield.
(B) Passing them through heavy water.
(C) Elastic collision with heavy nucleus
(D) Applying a strong electric field.​

Answer 1

Answer:

8. A

9. D

Explanation:

Answer 2

Answer:

8) D.

9) B.

Explanation:

8) Because if we consider earth and the ball as a system, linear momentum should be conserved.....hence, if ball moves up, earth moves down...and overall (net) momentum is zero....

9). Fast neutrons can easily be slowed down by passing them through water because of the 'collision' between neutron and hydrogen nucleus present in water.........

(applying a strong electric field won't help as neutrons aren't charged bodies and won't be affected by the current... however strong it may be...)

Hope this helps ☺️

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