i have a question abt the motion of objects when they r droped 4 a height?

Question

if a object is droped 4 a hot air ballon moving up at a contant speed then why does the object first moves upwards and then goes down

Answer 1

Newtons first law of motion states that an object continues in its state of rest or uniform motion in a straight line unless compelled by an external force to act otherwise. The object dropped continues to move upwards in obedience to this law then the gravitational force overcomes the upward force and it starts to fall.

Answer 2

Let the balloon be moving up with a speed of 9.8 m/s. The object in the balloon is also moving up with this speed.

At time t = 0 the object is dropped. But at this time t=0, it possesses an upward velocity of 9.8 m/s.

From this time it cannot move with the speed of 9.8 m/s. Its velocity reduces because gravity pulls it down with an acceleration of 9.8m/s^2.

The velocity of the object becomes zero only after one second.

Distance moved up during this one second is [9.8 + 0] / 2 * 1 = 4.8 m

From the point of dropping of object, the object moves up through a distance of 4.8 m and is at rest instantaneously and returns back.

However for an observer inside the balloon things will be different.

From the instant of dropping the object, he moves up with greater velocity than the object. Therefore, the distance between the balloon and the object will be increasing for ever and he will say the object falls down and never comes up.

Answer 3

The answer above is fine but technically we should say the object dropped still retains the momentum it had when it was in the balloon.

Objects in motion tend to stay in motion. Objects at rest tend to stay at rest. This is the concept of inertia.

Answer 4

When it was in the balloon, it was moving with the balloon's speed. So when it leaves the balloon, it still has that speed. It then slows down, until it stops instantaneously and starts to fall.