Question

In which of the following cases, the objects mentioned are in free fall, assuming no friction or air resistance?

1. An object dropped from a certain height
2. An object is thrown upward
3. Flying in an aircraft
4. A car accelerating at $9.8m{s}^{-2}$ on the road

• A. Only 1^st
• B. Only 3^rd
• C. 1^st and 2^nd both
• D. 1^st and 3^rd both

Answer 1

The correct option is C

1^st and 2^nd both

Freefall is any motion of a body where its weight is the only force acting upon it.

As per the definition of the free fall:
In the 1^st scenario, an object is moving downwards, due to its weight (gravitational force of attraction). There is no other force acting on it except its weight or gravitational force. So, it is a free fall.

In 2^nd scenario, an object is thrown upwards. While throwing the object, some external force will be exerted on the object to make it move upwards, but once it is released into the air, the external force disappears and no force will act on it except its own weight (which is the gravitational force exerted on the object by earth). So, it is said to be in free fall.

In the 3^rd scenario, aircraft moves horizontally or vertically due to its engine power (force). Since weight is not the only force acting on it, it is not in free fall.

In the 4^th scenario, the car is accelerating at $9.8m{s}^{-2}$ with the help of its engine power (force). Thus, it is not a free fall since its weight is not the only force acting on it.