What types of balls bounce?

Answer 1

Studying the mechanics of bouncing balls is a good way to learn simple physics.

Bouncing ball

We can all look back at our childhood memories and find a ball that bounces in some shape or form. Whether we played soccer with friends or threw a tennis ball against the wall. We have all played with these bouncy toys.

Although balls are fairly inconspicuous objects for most people, they actually serve as an interesting springboard for learning about many interesting physical phenomena. Acceleration, speed, energy; All of this can be learned by studying the physics behind bouncing balls.

There are essentially seven phases in each ball bounce, into which the action can be divided during the movement, before, during and after the impact investigation.

We will first look at the seven simplified phases of bouncing the ball, ignoring any external forces other than gravity. We will break down each step in detail with equations and yes (for the physicists among you), we have simplified a lot of things. Please find it for us. A little sneak peek: If you need a deeper understanding, the following video will be the one for you.

Level 1: Fall

The first stage is the start of each ball, in which the potential energy of the height of the ball is converted into kinetic energy by the acceleration of gravity. In a simplified case, the ball falls according to the force of gravity, which is always directed directly downward. On earth, this acceleration of gravity is 9.8 m / s2 (g = 9.8 m / s2). This essentially means that the speed of the ball accelerates at 9.8 m / s per second of fall.

Step 2: First contact

The first phase of contact is just that; when the ball is just in contact with the ground surface it will continue to fall under the influence of gravitational acceleration, but now a normal force from the ground surface, counteracting the force of gravity, will act on the ball.

Stage 3: Deceleration / negative acceleration

After the first impact, the ball decelerates or accelerates rapidly in the negative direction. The velocity of the ball continues to point downward when it is deformed, but the acceleration of the ball begins to point upward again when the reaction forces overcome gravity.

Step 4: Maximum deformation

After the deceleration phase, the ball has reached the maximum deformation. At this point the velocity is zero and the acceleration vector points upward. This is the lowest point of the ball and its maximum deformed point. If we assume that the ball is fully elastic and ignore other energy losses such as sound and heat, the ball will bounce back to its original drop height after this point.

Compression and decompression of a bouncing ball

Stage 5: Initial bounce

In this phase, the ball begins its journey back to the starting point. Its velocity and acceleration vectors point in the same direction, that is, up. The ball is less deformed than in the maximum deformation stage and now, due to its elasticity, it presses against the surface with a force greater than its own weight. This makes the ball bounce upward.

Stage 6: Zero Contact Bounce

With zero contact bounce, the ball is no longer deformed and barely touches the surface, essentially only at one point. The velocity moves the ball upward, but at this point the acceleration changes to counteract the velocity vector.

This is because the elasticity of the ball pressing on the surface no longer exerts a force that accelerates it upwards. The acceleration due to gravity pulling down is now the only force acting on the ball in a perfect system.

Stage 7: Full bounce

At the moment of full bounce, the ball has left the surface and its velocity vector is still pointing upward, although it is constantly decreasing due to the acceleration or deceleration of gravity. After this step, the ball reaches its peak in a new step where its velocity vector is zero and the only force acting on it is gravity.

Added variables and special cases in bouncing ball physics

The ball bouncing on top case has been simplified to eliminate, among other things, all other forces such as air resistance, imperfect elasticity, spin, friction, and the force of a first throw. All of this means that the physics of the bouncing ball gets complicated from here.

If the balls have some kind of spin, as is often the case when they are thrown, and if the surface they hit is not smooth, the spin of the ball is reversed from before to after impact. This is due to the force of friction.