Bouncing ball and coeff. of restitution

In summary, the conversation discusses the importance of measuring the initial height of the ball in a coefficient of restitution lab and how it can affect the accuracy of the results. It is agreed that as long as the distance travelled by the ball on each bounce is recorded, the reference point for measurement does not matter. However, it is important to avoid measuring the compressed top of the ball for accurate results.
  • #1
fisico30
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0
Dear Forum,

in the coefficient of restitution lab, a ball is drop from a certain height and the bounce height is measured to eventually calculate the coefficient of restitution COR...

Why should the initial height always be measured from the bottom of the ball and not from the top? Why does it matter? Does it give more precise results?

It should not matter as long as the bounce height is recorded using the top of the ball as reference...

thanks
fisico30
 
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  • #2
You want to know how far the ball drops and bounces back up (the distance travelled) on each cycle. If you're measurements also include the balls "height" at the moment of contact with the ground, then it doesn't matter where you take your measurements from, as long as you're recording the distance vertically traveled on each bounce. You'd need to avoid measuring the top of the ball when it is compressed.
 

1. What is the coefficient of restitution?

The coefficient of restitution is a measure of the elasticity of a bouncing object. It is the ratio of the final velocity to the initial velocity of the object after a collision with another object or surface.

2. How is the coefficient of restitution calculated?

The coefficient of restitution is calculated by taking the square root of the ratio of the rebound height to the drop height of a bouncing object. It can also be calculated by dividing the final velocity by the initial velocity.

3. What factors affect the coefficient of restitution?

The coefficient of restitution can be affected by the material and surface properties of both objects involved in the collision, as well as the angle and speed of the collision. Temperature and air pressure can also play a role in the coefficient of restitution.

4. How does the coefficient of restitution affect the bounce of a ball?

The higher the coefficient of restitution, the more elastic the ball is and the higher it will bounce. A lower coefficient of restitution means the ball is less elastic and will have a lower bounce. The coefficient of restitution also determines how much energy is conserved during a collision, with a higher coefficient indicating more energy conservation.

5. What is a "perfect" coefficient of restitution?

A perfect coefficient of restitution would be 1, meaning all of the energy from the initial impact is conserved and the object bounces back to the same height as the initial drop. In reality, most objects have a coefficient of restitution less than 1 due to energy loss from factors such as friction and air resistance.

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