Physics - Study Mode

[#676] A hunter on the ground wishes to shoot a bird on a tree at a distance with his rifle. He has to point the rifle
Correct Answer

(B) At a higher elevation than the bird

Explanation

Solution: A hunter on the ground wishes to shoot a bird on a tree at a distance with his rifle. He has to point the rifle at a higher elevation than the bird.

[#677] Force of impact is the force
Correct Answer

(C) When the objects meet

Explanation

Solution: Force of impact is the force when the object meets.

[#678] A rubber ball is dropped from a height of 2 metres. To what height will it rise if there is no loss of energy/velocity after rebounding ?
Correct Answer

(C) 2 metres

Explanation

Solution: The potential energy of a body when raised through height h is given by mgh. Each time, a normal rubber ball hits the floor, it loses one-fifth of its total energy and the rebound height is proportional to energy, so each bounce will rebound to four-fifth of the previous bounce. But, the question states that there is no loss of energy/velocity after rebounding. So the height of 2 metres will be maintained.

[#679] A piece of paper and a cricket ball are dropped from the same height. Under which of the following conditions do both reach the surface simultaneously ?
Correct Answer

(D) They must be dropped in vacuum

Explanation

Solution: When a piece of paper and a cricket ball are dropped from the same height, they reach the surface at different time because the shape of the paper is more flat and it behaves like a parachute causing more air resistance acting on it with respect to the ball. But, in order to reach the surface at the same time by both the articles, they must be dropped in vacuum. It is because in vacuum there is no other force other than force of gravity occurring on them and this leads to a conclusion that both the article reaches at the same time.

[#680] Angle of friction and angle of repose are
Correct Answer

(A) Equal to each other

Explanation

Solution: Angle of friction and angle of repose are equal to each other.