# A Practical Application of the Fundamentals of Physics.

Gravity, the force that attracts a body toward the center of the Earth, seems to be out to get me. I have been described as being “made out of fall down”. This is because I fall down. A lot. I have long legs and big feet and sometimes I don’t pick them up, so I trip. I ride my bike to work a lot and sometimes the potholes get me. Occasionally my adventures in science result in mystery bruises. Bruises and scrapes I can handle, but recently I had the opportunity to test some of Newton’s Laws in other ways.

I, in my little Dodge Caliber, was hit by a GMC pickup truck. After I took a hot minute to get my wits about me, I crawled out and looked at was left of the tail end of my car. My first thought? “Good job, crumple zones. Good job….” This is how we got to this blog entry. It’s been a while since High School Physics, so let’s all get caught up on some basics:

• Inertia is the tendency of an object to resist any change in its velocity (speed+direction).
• A fancier way to say that? Newton’s First Law of Motion states that a body at rest remains at rest unless acted upon by an external force and a body in motion continues to move at a constant speed in a straight line unless it is acted upon by an external force.
• Force = Mass x Acceleration (if Acceleration is the rate of change of the velocity)

In other words, unless some outside force acts on an object it will keep on going or staying, as the case may be. One of those outside forces is friction. Which brings us to inertia. A bigger, heavier object will take longer to get to a high rate of speed, but if the same force is applied, it will also take a longer time to slow down too. So a ping pong ball takes a lot less effort to stop than a freight train, but it also takes a lot less effort to throw a ping pong ball than it does a freight train. And so that brings us to the practical application portion of today’s blog.

Specifically, in the case of my accident, my little car had almost come to a stop when I was hit from behind. Since the truck was so much bigger, the truck had more momentum than my car brakes could handle—so I was pushed forward, even though the truck slowed significantly.

Even though there was a lot of damage done to the rear end of my car, I was still safe. This is because some physicists and engineers (thank you!) have been working to make vehicles safer. To do this, they have to take into account Newton’s Laws of Motion. Some of the safety features cars have these days are seat belts, crumple zones, air bags and specialized tires. Since you can’t instantaneously change the mass of the vehicles in an accident, your best bet is to change the acceleration to reduce the force. The function of the seat belts, crumple zones and air bags is to do just that by slowing things down more gradually. They change the acceleration of the person inside the vehicle by increasing the time it takes for the accident to occur – even if it is just by fractions of seconds.

Seatbelts comprise about 50% of your protection in a car. When a driver stops the car suddenly, the driver tends to lunge forward, because the driver’s body tends to maintain its speed and direction. The seat belt holds the driver and prevents the driver from flying forwards when the car stops. Seat belts help by applying a force that overcomes your inertia as in Newton’s First Law. They also increase the time in the wreck which results in a lesser impact force on you; more time means less acceleration to you! Even when your body comes to a stop, however, your internal organs continue to move, slamming against each other because of the impact. So, that’s fun.

Good tires are also an important safety feature on your car. The friction between the tires and the road determines the maximum acceleration and the minimum stopping distance. If the surface of a tire is rougher, then the friction force is larger. This is super important if you are slamming on your brakes to avoid something or speeding up, also to avoid something.

Prior to 1959, people believed the more rigid the structure, the safer the car. This ended up being deadly because the force from the impact went straight to the passenger. Crumple zones are specially engineered areas on your car that are designed to absorb energy as they are crushed and slow down the rest of the car more gradually. They absorb energy from a collision and therefore reduce the force of a collision on the passengers. They aren’t just spots that are softer or less dense on the car, they are specifically engineered to crush in a relatively gradual and predictable way that absorbs much of the impact energy, keeping it away from the occupants in what is termed a “controlled crush”.

So! Buckle up and be safe, and good job, crumple zones…good job.

# Sports Science: Olympics Edition ‒ Gymnastics

Every four years, the eyes of the world shift towards a global competition, complete with feats of strength, determination, talent and teamwork. The Summer Olympics are back, and I could not be more excited. The following post is one of three about some of my favorite events.

The spotlight was on Gabby Douglas four years ago in London, as the American led the “Fierce Five” to a Gold Medal in the team gymnastics competition and earned Gold again in the individual all-around competition. This go-around, Douglas has taken a backseat to Simone Biles, a resident of Spring, TX and the favorite to win the individual all-around competition in Rio de Janeiro.

One of Biles’ best events is the balance beam, in which she has won individual Gold Medals at the World Championships the last two years. To earn the most points in this event, the gymnast must risk the most while avoiding a slip or fall.

Maintaining your balance in everyday life is a case study in the physics concept called center of gravity. The center of gravity of an object is the singular point where all the components of the forces of gravity acting on the object balance out. If you grab a pencil and try to balance it on your finger, the point where it does not fall off either side is its center of gravity. The center of gravity of the human body is around the belly button; as long as the body’s center of gravity is over the person’s feet (or whatever part of the body is touching the ground), the person will remain upright.

The concept of center of gravity is how tightrope walkers stay on the rope. Usually, a tightrope walker will hold a long stick perpendicular to the rope; this spreads out the total weight and lowers the center of gravity of the person, making it more difficult to be knocked to one side. It’s much more difficult to knock over a bowl than a tall glass. As a result of the lower center of gravity, tightrope walkers have a generally easy time walking across!

However, this trick does not work on the balance beam. Biles and other gymnasts must have complete control of their center of gravity to keep from falling over to one side, and the space they have to balance over is thinner than the width of most people’s feet.

An Olympics regulation balance beam is five meters long but only 10 centimeters wide and held 125 centimeters off the ground. There is very little room for error. Simple maneuvers like turning 180⁰ can go horribly wrong with a slight movement. More complicated maneuvers like handsprings and free aerial cartwheels (both part of Biles’ routine at the 2016 Pacific Rim Championships) require hours of meticulous practice to avoid a fall.

To complete those maneuvers, Biles relies on the concept of angular momentum. This is the idea that a spinning object will keep spinning at the same rate unless acted upon by an external force. Basically, for the optimum spin on a handspring or cartwheel, the gymnast must rotate around her center of gravity. If she does so, she will continue the spin all the way round until coming back into contact with the beam.

With some natural talent, hours of practice and the help of some physics, Biles and Team USA is in prime position to bring home Gold Medals galore!

Gymnastics events at the Rio Games begin Aug. 6 and conclude Aug. 16.

# Happy Birthday, Isaac Newton!

Had he lived to see it, Sir Isaac would be 367 years old today – and probably pretty amazed at the scientific leaps and bounds we’ve seen since the 1687 publication of his Principia – widely regarded as one of the most influential books in the history of science.

Though he’s known to schoolchildren to world over as the recipient of a nasty bump on the head from a falling apple – the true origin of Newton’s conceptualization of gravity comes from a little higher in the sky. So, in honor of Sir Newton’s birthday, here’s a short clip from the BBC explaining how we came to know why we don’t just fall right off the Earth:

How do you remember Newton? Let us know in the comments.

And if you haven’t already, check out Google’s homepage today for their celebration (be sure to scroll over the image to get the full effect).

UPDATE: According to Scientific American, the apple story is not as apocryphal as some have claimed. (via BoingBoing)

# Girls Exploring Math and Science at HMNS this Saturday!!

It’s National Engineers Week and what that means for us is that it’s almost time for GEMS 2009 here at the Houston Museum of Natural Science.

The Girls Exploring Math and Science event has been hosted at the Houston Museum of Natural Science since 2006 and we’re all geared up for this year to be so much fun. We have Girl Scouts hosting booths on hands-on topics ranging from catapults and gravity to probability and electricity!

Our Community partnership with the Girl Scouts of San Jacinto Council has drawn in more and more girl scouts from across the council each year to come up with exciting topics to study and share with the GEMS visitors on Saturday during the event. We have also invited other groups from the community to host booths in the Grand Hall of the Museum and share their love of Math and Science through hands on activities and information about their organizations.

The 2009 Community booths will include the Society of Women Engineers, MD Anderson Cancer Center, Baylor College of Medicine and the John C. Freeman Weather Museum among other great organizations with lots to share to our visitors!

So bring your family and join us for a fun event learning about Science, Engineering, Math and Technology here at the Girls Exploring Math and Science event on Saturday, February 21, 2009 from 9am – 12pm.

Come early so that you can beat the Saturday crowd, see all of the great booths and really enjoy the event!

(I would also definitely suggest buying your tickets online at www.hmns.org so you can just jump right in on Saturday and avoid the box office line!)