why does ball bounce when we throw the ball on ground even when gravitational force is acting on it.
why does ball bounce when we throw the ball on ground even when gravitational force is acting on it.
A ball will not always bounce from the ground upon falling. It will depend on whether or not the ground acts as an elastic medium or if the ball acts as an elastic medium. If one of them is not elastic, then the result is the ball will stick to the ground.
Some examples where the ball will not bounce back:
Example 1: If the ball is an egg. It will break upon hitting the ground and stay there.
Example 2: If the ball falls in soft mud. It will not bound back.
When will the ball bounce back:
If the ball and the ground are elastic, then the ball bounces due to a force proportional to its deformation. This can be quantified through an empirical law called Hooke’s law.
In the case of the ball, both the ground and the ball will oppose deformation. This will create a net force from the ground on the ball and an equal force from the ball towards the ground, since the ground won't yield, the ball will be thrown back up.
In case of elastic,
The ball is elastic - if you deform it (without breaking it), it will go back into its original state.
Let’s split up the trajectory in 4 pieces:
- The ball is in free fall. At the end of this, the ball touches the ground. The only force acting on the ball is by Earth (gravity).
- The ball is being stopped by the ground, but the ground will not yield. At the end of this, the ball comes to rest. This means that there are two forces acting on the ball:
2a) downwards by Earth (gravity) - this is a tiny force now, you might as well ignore it.
2b) upwards by the ground - this is a pretty big force in comparison. The effect of it is to deform a ball into a cross between a sphere and a pancake. - The ground now successfully stopped the ball - but the ball is a pancake! The ball is elastic, as mentioned above, and now is reshaping itself. The ground, however, still does not yield. There are two forces acting on the ball:
3a) downwards by Earth (gravity) - this is still a tiny force.
3b) upwards by the ground, counteracting the ball pushing downwards. This is now accelerating the ball (remember, the ball’s velocity has reached 0 at the end of part 2)
At the end of this, the ball just leaves the ground. - The ball now moves upwards! The only force acting on the ball is by Earth, pulling it downwards.
Incidentally, if you are wondering why I am saying that the force of gravity is tiny on the ball, think of how little contact it has with the ground. If you drop the ball and it falls for 1 second, it gets accelerated to 10 m/s by gravity. However, the velocity changes to about -10 m/s due to the contact with the ground - this happens almost instantly, let’s say, 10 ms. This means that the force is 200 times higher than gravity, as the change in velocity is twice is high and the time is 100 times shorter.
A ball will not always bounce from the ground upon falling. It will depend on whether or not the ground acts as an elastic medium or if the ball acts as an elastic medium. If one of them is not elastic, then the result is the ball will stick to the ground.
Some examples where the ball will not bounce back:
Example 1: If the ball is an egg. It will break upon hitting the ground and stay there.
Example 2: If the ball falls in soft mud. It will not bound back.
When will the ball bounce back:
If the ball and the ground are elastic, then the ball bounces due to a force proportional to its deformation. This can be quantified through an empirical law called Hooke’s law.
In the case of the ball, both the ground and the ball will oppose deformation. This will create a net force from the ground on the ball and an equal force from the ball towards the ground, since the ground won't yield, the ball will be thrown back up.
In case of elastic,
The ball is elastic - if you deform it (without breaking it), it will go back into its original state.
Let’s split up the trajectory in 4 pieces:
- The ball is in free fall. At the end of this, the ball touches the ground. The only force acting on the ball is by Earth (gravity).
- The ball is being stopped by the ground, but the ground will not yield. At the end of this, the ball comes to rest. This means that there are two forces acting on the ball:
2a) downwards by Earth (gravity) - this is a tiny force now, you might as well ignore it.
2b) upwards by the ground - this is a pretty big force in comparison. The effect of it is to deform a ball into a cross between a sphere and a pancake. - The ground now successfully stopped the ball - but the ball is a pancake! The ball is elastic, as mentioned above, and now is reshaping itself. The ground, however, still does not yield. There are two forces acting on the ball:
3a) downwards by Earth (gravity) - this is still a tiny force.
3b) upwards by the ground, counteracting the ball pushing downwards. This is now accelerating the ball (remember, the ball’s velocity has reached 0 at the end of part 2)
At the end of this, the ball just leaves the ground. - The ball now moves upwards! The only force acting on the ball is by Earth, pulling it downwards.
Incidentally, if you are wondering why I am saying that the force of gravity is tiny on the ball, think of how little contact it has with the ground. If you drop the ball and it falls for 1 second, it gets accelerated to 10 m/s by gravity. However, the velocity changes to about -10 m/s due to the contact with the ground - this happens almost instantly, let’s say, 10 ms. This means that the force is 200 times higher than gravity, as the change in velocity is twice is high and the time is 100 times shorter.
