1 / 23

# Bouncing Balls - PowerPoint PPT Presentation

Bouncing Balls. Introductory Question. If you place a tennis ball on a basketball and drop this stack on the ground, how high will the tennis ball bounce? To approximately its original height Much higher than its original height Much less than its original height.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

## PowerPoint Slideshow about 'Bouncing Balls' - efuru

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

### Bouncing Balls

• If you place a tennis ball on a basketball and drop this stack on the ground, how high will the tennis ball bounce?

• To approximately its original height

• Much higher than its original height

• Much less than its original height

Observations aboutBouncing Balls

• Some balls bounce better than others

• Dropped balls don’t rebound to their full height

• Balls bounce differently from different surfaces

• Ball bounce differently from moving objects

• Why can’t a ball that’s dropped on a hard floor rebound to its starting height?

• Why does the floor’s surface affect the bounce?

• How does a ball bounce when it hits a bat?

• What happens to the bat when a ball hits it?

• Why can’t a ball that’s dropped on a hard floor rebound to its starting height?

• What happens to ball’s energy as it bounces?

• As it strikes a rigid floor, a ball’s

• kinetic energy decreases by the “collision” energy

• elastic potential energy increases as it dents

• As it rebounds from that surface, the ball’s

• elastic potential energy decreases as it undents

• kinetic energy increases by the “rebound” energy

• Rebound energy < collision energy

• A “lively” ball wastes little energy as thermal energy

• A “dead” ball wastes most of its energy

• Coefficient of Restitution

• is a measure of a ball’s liveliness

• is the ratio of outgoing to incoming speeds:

coefficient of restitution = outgoing speed / incoming speed

• Why does the floor’s surface affect the bounce?

• Both ball and floor dent during a bounce

• Work is proportional to dent distance

• Denting floor stores and returns energy

• A “lively” floor wastes little energy

• A “dead” floor wastes most of its energy

• A floor has a coefficient of restitution, too

• A soft, lively floor can help the ball bounce!

• How does a ball bounce when it hits a bat?

• Do both the ball and bat bounce?

• Incoming speed → approaching speed

• Outgoing speed → separating speed

• Coefficient of Restitution becomes:

coefficient of restitution = separating speed / approaching speed

Ball and Bat (Part 1)

• Ball heads toward home plate at 100 km/h

• Bat heads toward pitcher at 100 km/h

• Approaching speed is 200 km/h

Ball and Bat (Part 2)

• Approaching speed is 200 km/h

• Baseball’s coefficient of restitution: 0.55

• Separating speed is 110 km/h

Ball and Bat (Part 3)

• Separating speed is 110 km/h

• Bat heads toward pitcher at 100 km/h

• Ball heads toward pitcher at 210 km/h

Introductory Question (revisited)

• If you place a tennis ball on a basketball and drop this stack on the ground, how high will the tennis ball bounce?

• To approximately its original height

• Much higher than its original height

• Much less than its original height

• What happens to the bat when a ball hits it?

• A bouncing ball transfers momentum

• while stopping

• while rebounding

• A livelier ball transfers more momentum

• A bouncing ball can also transfer energy

• These two transfers together govern bouncing

• A ball transfers momentum and energy to a bat

• Identical elastic balls can transfer motion perfectly

• Harder surfaces bounce faster

• Momentum is transferred more quickly

• Time is shorter, so force is larger

• No one likes bouncing off hard surfaces

• The ball pushes the bat back and twists it, too

• When the ball hits the bat’s center of percussion,

• the bat’s backward and rotational motions balance

• the bat’s handle doesn’t jerk

• When the ball hits the bat’s vibrational node,

• the bat doesn’t vibrate

• more energy goes into the ball

• Each ball has a coefficient of restitution

• Energy lost in a bounce becomes thermal

• The surface can affect a ball’s bounce

• Surfaces bounce, too