Physics · Motion In A Straight Line · NEET
No. Free fall only means the sole force is gravity, so the acceleration is g. The object can start from rest (dropped), can be thrown down, or can be thrown up. In all three cases it is in free fall because after it leaves the hand only gravity acts. NCERT defines free fall exactly this way: an object released near the Earth is accelerated downward by gravity, and if air resistance is neglected it is in free fall.
Yes. Once the ball leaves your hand, the only force on it is gravity (ignoring air), so it is in free fall the whole time: while rising, at the top, and while coming down. Its velocity decreases going up, becomes zero at the top, then increases going down, but the acceleration stays g downward throughout. This is why the up-and-down trip is symmetric.
No. In free fall the acceleration is g for every object regardless of mass. A 1 kg ball and a 5 kg ball dropped together hit the ground at the same time. The reason is that a heavier object has more gravitational force but also more inertia, and the two effects cancel exactly. Heavier things seem to fall faster only when air resistance matters, which free fall ignores.
g is a magnitude, always +9.8 m/s2 (or +10). The sign in your equations depends on the direction you call positive. If you take upward as positive, then acceleration a = -g. If you take downward as positive, then a = +g. Fix your positive direction first, then give velocity, displacement and acceleration matching signs. This sign choice is covered fully in the next concept.
An object in free fall feels weightless because everything around it accelerates at the same rate g, so there is no supporting normal force. But the object still has weight mg pulling it down; that force is exactly what causes the acceleration. So free fall causes the sensation of weightlessness, but the gravitational force is very much present.
A ball is thrown vertically downward with a velocity of 20 m/s from the top of a tower. It hits the ground after some time with a velocity of 80 m/s. The height of the tower is (g = 10 m/s2):
A ball is thrown vertically upward with a velocity of 4 m/s from a bridge. The ball strikes the water surface after 4 s. The height of the bridge above the water surface is (g = 10 m/s2):
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Free fall is the motion of an object when the only force acting on it is gravity, with air resistance neglected. Such an object moves with constant acceleration g = 9.8 m/s2 directed downward, regardless of its mass.
g = 9.8 m/s2 is the standard value, but many NEET and NCERT numericals use g = 10 m/s2 to simplify arithmetic. Always read the question, it tells you which value to use.
Yes. As soon as it leaves the hand, only gravity acts, so it is in free fall while rising, at the top, and while falling. The acceleration stays g downward the whole time.
The three equations of motion with a = g: v = u + gt, s = ut + (1/2)g t^2, and v^2 = u^2 + 2gs. Just replace a with g (using the correct sign for your chosen positive direction).
Free fall is a direct source of easy scoring numericals on tower, bridge and dropped-object problems. It also builds the sign-convention skills needed for the whole kinematics chapter, so mastering it protects marks across many questions.
