Why Do Objects Bounce When They Hit the Ground?

  • Context: High School 
  • Thread starter Thread starter amolv06
  • Start date Start date
  • Tags Tags
    Bounce
Click For Summary

Discussion Overview

The discussion revolves around the mechanics of why objects bounce when they hit the ground or a wall. Participants explore concepts related to kinetic and potential energy, forces involved in bouncing, and the role of material properties such as elasticity and compressibility. The scope includes theoretical explanations and conceptual clarifications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions the nature of the force that transforms potential energy back into kinetic energy during a bounce.
  • Another participant identifies the "normal" force as the upward force exerted by the ground in response to the downward force of the ball.
  • A participant mentions elasticity as a contributing factor to bouncing, referencing elastic collisions.
  • One contributor suggests that the forces at play are primarily electromagnetic, specifically electric forces between molecules, which contribute to the potential energy during compression.
  • Several participants emphasize the importance of the compressibility of the ball compared to the ground, noting that materials like clay do not bounce as well due to their inability to return to shape quickly.
  • There is a discussion about the behavior of different materials, such as rubber and steel, and how their properties affect bouncing on various surfaces.
  • One participant points out that while deformation occurs during a collision, the extent of energy loss due to heat or deformation varies and influences the bounce.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the forces and properties involved in bouncing. There is no consensus on a singular explanation, as different aspects of the phenomenon are highlighted by various contributors.

Contextual Notes

The discussion includes assumptions about the nature of forces and material properties, and there are unresolved questions regarding the specifics of energy transformation and the role of different forces in the bouncing process.

amolv06
Messages
45
Reaction score
0
This is probably a stupid question, but why is it that things bounce back at you when they hit the floor or a wall? When the kinetic energy is transformed into potential energy as the ball compresses, is there a force that transforms the potential energy back into kinetic energy? From my extremely limited understanding, potential energy requires a force to be turned into kinetic energy -- i.e., gravitational potential energy is turned into kinetic energy by gravity. What is the force that acts on a bouncing object?
 
Physics news on Phys.org
The force is called the "normal" force. According to Newtons second law every force has a counter force. So when the ball exerts a downward force on the ground the ground exerts an upwards force (called the normal force) on the ball. But since the ground is so heavy it barely moves, the ball on the other hand flies back up.
 
The force is electromagnetism between the molecules of the object... The magnetic force I believe is insignificant in magnitude compared to the electric force... so essentially it is electric forces...

ie: the potential energy that the kinetic energy is converted to is: electric potential energy.
 
Okay, I don't know any physics, but isn't it important that the ball be compressible, while the ground is not? The ball is not only compressible, but it returns to it's original shape quickly. Isn't that why it bounces? Clay won't bounce much...

A rubber ball will bounce on a steel surface, and steel balls bounce on a rubber surface.

I guess the rubber ball is pushing the Earth a little when it returns to it's original shape... but it's not enough to matter.

Pool balls also bounce, but isn't that because they are in an environment (the pool table) with a small amount of friction?
 
futurebird said:
Okay, I don't know any physics, but isn't it important that the ball be compressible, while the ground is not? The ball is not only compressible, but it returns to it's original shape quickly. Isn't that why it bounces? Clay won't bounce much...

A rubber ball will bounce on a steel surface, and steel balls bounce on a rubber surface.

I guess the rubber ball is pushing the Earth a little when it returns to it's original shape... but it's not enough to matter.

Pool balls also bounce, but isn't that because they are in an environment (the pool table) with a small amount of friction?
Actually, elasticity isn't directly related to deformation. Steel is extremely elastic, so a steel ball will bounce very well on any hard surface (as long as the force is below the plastic deformation limit).
 
Pool balls are also elastic, and bounce very well on a hard surface that isn't deformed by the impact of the pool balls. I've seen the results of this at a friends house.

There's always deformation in a collision, it's only a question of how much energy is lost through the collision process to heat, or deformation at the time contact ceases.
 

Similar threads

  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 7 ·
Replies
7
Views
1K
Replies
8
Views
2K
  • · Replies 54 ·
2
Replies
54
Views
7K
  • · Replies 9 ·
Replies
9
Views
2K
Replies
6
Views
2K
  • · Replies 12 ·
Replies
12
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K