**Physics of Sports Outline**

Linda Valerio

**Introductions:**

Why am I here? (For World Year of Physics.)

What is Fermilab, and what is my job there?

Now, on to the Physics of Sports!

**Start simple -- motion of a ball:**

Physics explains the very small, the very large, and what is right in
front of us every day.

Let's start with a simple ball in motion. (dribble basketball)

We've all seen this before, but what makes it work?

Explain Potential/Kinetic energy cycle, then conservation of energy.

Losses at bottom are reason additional force needed to dribble.

Flight path of ball.

Break down motion of free-throw into right-angle vectors.

Explain that thinking this way makes it possible to predict motion with
mathematical equations. (don't actually show equations)

Briefly mention air resistance, will cover more later.

This also applies to soccer and volleyball. Can always predict motion
using this method.

Show soccer clip and invite them to imagine the vector arrows as ball
get re-directed.

**Focus on equipment #1:**

Discuss why basketball, soccer ball, volleyball, and football all have
different features and compare to each other.

Examples:

Soccer ball tough (gets kicked a lot) and not especially bouncy (want to
keep it near you when you stop it)

Volleyball seams help make ball harder to return ("dances" in flight
path if hit right)

Basketball especially bouncy (bounce passes, dribbling, shooting off
backboard)

Be sure to mention grip texture for basketball and football.

Shape of football: enables spiral pass (discuss also conservation of
spin) and keeps ball from rolling too far when dropped (because yards
must be measured)

Discuss conservation of spin -- ball wants to keep spinning.

Catch football between body and arms to keep from spinning away. (and
keeps opponents from getting it)

Stress that every feature has a function.

**Motion of a ball with striking object:**

The rules are still the same when we strike a ball with an object. We
can still think in terms of vectors and use equations to predict motion,
even though it is more complicated.

Briefly explain golf swing and transfer of energy (conservation of
momentum).

Show golf clip and repeat main ideas as they occur (talk over music).

Add that ball is going 150 MPH.

End of clip shows follow-through. Explain why this is necessary. (longer
contact time = maximum force transmitted)

It can get even more complicated (show baseball clip)

Vectors shown for home run hit (same rules for vector breakdown and
conservation of momentum still apply even though more motion to
describe)

Discuss energy in baseball/bat collision (and tennis ball/racket
collision)

Small mass object can damage larger one if speed great enough. (compare
to car crash)

Ask what happens when we hit in wrong spot. Bat/racket jolts our grip.
Loss of energy felt in injury to hands, wrist, forearm, etc. Not only
does it hurt, but energy to return ball is being wasted.

Hockey is most challenging: player, stick and puck all in motion. Rules
still apply.

Another interesting point in hockey: How to get puck moving fast (120
MPH) without bringing stick high like a golfer? Explain slapshot.
(buildup of PE and sudden release)

Show hockey clip.

**Focus on equipment #2:**

Repeat that speed of striking instrument and ball are factors in motion.

Materials of striking instrument and ball are also factors.

Repeat importance of follow-through.

Golf ball is dimpled -- helps air flow around ball (reduces air
resistance -- link to Newton's third law) and keeps flight path
straight.

Seams on baseball allow pitcher to throw difficult pitches.

Tennis ball deflects easily -- spreads force onto larger area of racket

Puck is flat to glide along ice rather than roll (things don't roll well
on ice)

**On to sports without throwing or striking...**

**Drag:**

Look at photos of cycling, swimming, speed skating.

What is in common? (Tight clothes and postures reduce forward surface
area)

Done to reduce air/water resistance to motion, also known as drag.

If drag is reduced, then more of the athlete's energy goes toward
forward motion.

Drag increases with surface area and speed.

This is a factor in all sports, but especially important for speed
sports like these.

**Focus on equipment #3:**

Swimming -- Speedo studied shark skin to produce special fabric. Suit
has less drag than human skin/hair.

Cycling -- helmet protects head but also reduces drag.

Speed skating -- wear helmet or hood to streamline head.

Also note trail in ice behind blade. For all types of skating, force
through blade melts ice into very thin film of water that acts as
low-friction lubricant. Water so thin it re-freezes after skater passes.

**Friction:**

Again, important factor in all sports.

Especially important in rock-climbing.

Powder used to absorb moisture and increase friction of skin (opposite
of swimming)

Powder also used in gymnastics.

Still to absorb moisture, but reduces friction of skin so it moves
freely over equipment

If done without chalk, hands turn red and hurt -- energy going into body
instead of toward motion.

Sprinters -- drag and friction both important

Starting blocks -- imagine vector motion mostly horizontal at start

Newton's 3^rd^ law again: blocks point body toward finish line so first
few steps more horizontal than vertical.

Also, less drag if body not upright.

Friction: remind how walking works.

Sprinters exert much more force, and danger of slipping if friction not
great enough.

Use spikes to grip track, no wasted energy.

Marathon runners use regular shoes (usually on pavement, and less force
exerted)

**Spinning bodies:**

Revisit principles in football spin (conservation of spin - wants to
keep spinning)

Imagine how much force it takes to stop spin of larger mass, like body
in martial arts.

Show martial arts clip.

Figure skating.

Discuss how location of mass relative to spinning axis affects speed of
spin.

Also discuss position of hands at start, in air, and prior to landing of
spinning jump.

Show gif files in motion.

Get volunteer to demonstrate with turntable and weights.

**Reaction time:**

Again, important to all sports.

Tennis: Venus Williams serves 127 MPH. Must react quickly.

Show tennis clip.

Skiing, around 80 MPH.

Must react quickly if unexpected object in path or collide with
rock/tree.

Baseball.

May seem slow at times, but not really.

400 ms between release of pitch to over home plate.

Go through details shown on slide.

Get volunteer to test reaction time with ruler drop.

Show table and compare to timing required to hit fastball pitch in
baseball.

**Summary:**

Repeat main point: Laws of physics apply to all sports.

Can use this to improve skills.

Can also make career of designing sports equipment.

Invite them to visit Fermilab for both recreation and science.

Ask for questions and offer for teacher to contact if questions later.

**Approximate time: 40-45 minutes**

**Tips:**

Give rulers to all volunteers as "gift" when they are finished.

If passing out rulers to all members of class, do so at very end of
presentation and put calculation table up again.