Question

A bullet is fired horizontally from a rifle at a distant target. Ignoring the effects of air resistance, which of the following are values of horizontal acceleration and vertical acceleration?
(A) $10m{s^{ - 2}}\& 10m{s^{ - 2}}$
(B) $10m{s^{ - 2}}\& 0m{s^{ - 2}}$
(C) $0m{s^{ - 2}}\& 10m{s^{ - 2}}$
(D) $0m{s^{ - 2}}\& 0m{s^{ - 2}}$

Answer 1

Hint:Figure out the forces that could be acting on the bullet in different directions and then calculate their horizontal and vertical components to find out the accelerations in those directions.

Complete step by step answer:
A bullet is fired horizontally from a rifle at a distant target. If no force is acting on the bullet, then it would continue to move along a straight line following the path in which the rifle was directed towards i.e. horizontally. But since forces are acting on the bullet it will be accelerating in certain directions in which the force is being applied on it.
According to the question there is only one external force that could be possibly acting on the bullet, that is the gravitational force due to its weight. The gravitational force would be accelerating the bullet in the vertical direction towards the ground and since no other forces are acting, it will follow a parabolic trajectory starting off horizontally and then continue to dip towards the ground. Since no other force is acting in the vertical direction other than the gravitational force of attraction, the bullet will be accelerated with only the acceleration due to gravity in the vertical direction.
In the question it is already mentioned that we ignore air resistance as it would be acting as a resistance in the horizontal direction, decelerating the bullet but since it is absent, so the horizontal acceleration of the bullet will be zero.
Therefore, we can finally conclude that the horizontal acceleration of the bullet will be zero while the vertical acceleration will be equal to the acceleration due to gravity of the earth i.e. $10m{s^{ - 2}}$.
Hence, option (C) is the correct answer.

Note: When a bullet is fired, the rifle experiences a shock in the backward direction. Due to this shock it might happen that the nozzle of the rifle moves slightly away from the horizontal direction and this would create acceleration components in both vertical and horizontal directions.