Question

For a projectile, the magnitude of acceleration
A.In the horizontal direction is zero
B.In the vertical direction is g.
C.Both A & B
D.In the vertical direction is zero.

Answer 1

Hint: We know that on a projectile only gravitational force acts. The direction of gravitational force of earth is always downward. Thus, gravitational acceleration acts only in a vertically downward direction.

Complete answer:
As we know that a projectile is any object upon which the only force which acts on it is gravity. An object that once projected or dropped continues to be in motion by its own inertia and is influenced only by the downward force of gravity provided that the influence of air resistance is negligible is called a projectile.. Projectiles follow a parabolic trajectory due to the influence of gravity on the body which continuously tries to push it downwards. There are no horizontal forces acting upon projectiles, so the horizontal velocity of a projectile is constant. Hence, no horizontal acceleration. The only force which acts on a projectile is gravitational force, which acts vertically downwards. Therefore, vertical acceleration caused by gravity is g and its value is 9.8 m/s. The horizontal motion of a projectile does not depend on its vertical motion. So, we have arrived at the conclusion that the magnitude of acceleration in the horizontal direction is zero whereas in the vertical direction is ‘g’.
So, Option (A) and (B) both are correct.

Hence, Option(C) is correct.

Additional information:
The range of the projectile,the maximum height and Time of flight attained by the projectile both are highly influenced by acceleration due to gravity ‘g’. It can be understood easily with the help of the formula.
Range of the projectile=$R=\dfrac{{{u}^{2}}\sin 2\theta }{g}$
Height of the projectile=$H=\dfrac{{{u}^{2}}{{\sin }^{2}}\theta }{2g}$
Time of flight=T=$T=\dfrac{2u\sin \theta }{g}$

Note:
One must remember all the above formulas to solve questions of projectile motion. We must also note that these formulas are derived by assuming that opposition of air to the motion of the body is negligible. Similarly, Acceleration due to gravity changes from place to place , so we can get slightly different values at different places.