Physics Fun Fact of the Day - June 1

Physics is Fun :)

Light has weight. The weight of sunlight on the earth's surface has been determined to be two pounds per square mile.

The Physics in Hurdling

When training for a hurdles event, it is crucial to have an even running tempo, so that the number of steps between hurdles can be calculated. If the hurdler "stutter-steps", or takes a series of smaller steps in the approach, he/she will lose momentum, and therefore the take-off speed after the hurdle will be slower, and the race ultimately lost.

The average take-off distance is six to seven feet from the base of the hurdles. By taking off a long way in front of the hurdles, it is possible to obtain a large range while maintaining a low vertical height. The hurdler lands approximately three feet (1 meter) past the hurdle, so maximum height must be reached before clearing the hurdle. This also ensures a faster take-off time, as there is less time in the air, where there is not horizontal velocity gained.

The motion of hurdling over the object is an example of projectile motion where a person will jump at a certain launch angle and land at that same angle on the other side of the hurdle. For hurdling, the smaller the angle of take off, the less time it will take to pass over the hurdle but also with a smaller angle comes a greater distance covered. One must make sure to reach a height over the hurdle but not too high over the hurdle that you gain "hang time" and lose a precious second.

Right before the hurdle your knees act like springs and compress a certain distance, build energy (this is called potential energy of a spring), and release it into kinetic energy over the hurdle. When landing, the springs that are your knees take the impact, conserve the energy once again, and release it towards your run.

Physics Fun Fact of the Day - May 31

Rotational speed around the Earth is also dependent on altitude above sea level, and a person at the top of a mountain on the Equator is actually traveling faster than 1,660 km/hr (as he has further to go with each revolution).

Physics Fun Fact of the Day - May 30

A person on the equator is rotating around the Earth at about 1,660 km/hr.

Physics Fun Fact of the Day - May 29

Electricity doesn't move through a wire but through a field around the wire.

Basketball - Spin on the Ball

Spinning the ball when you shoot is not done to affect air resistance, or to make air resistance cause the ball's path to curve, as is the case in baseball. Basketballs move too slowly for that to happen. Once the basketball leaves the shooter's hand, it travels in an unchanging parabolic path. So what's the purpose of backspin? Backspin on the ball is used to help it to bounce into the net when it hits the rim. It will usually hit something, unless the throw was very high. The backspin, after contact with the back rim or board, will result in a change in velocity opposite to the spin direction, changing an equal-angle rebound into a velocity more toward the net. This makes it more likely that the ball will go in.

The Forces in Running

If one were to make a free body diagram of a person while he or she is sprinting, there would be many forces acting upon him or her. First would be the weight force from the pull of gravity, the applied force from one's muscles moving in a direction to the right, friction going opposite of the applied along with drag, and a normal force opposite the weight force. All of these forces together would add up to a runner's acceleration.

Physics Fun Fact of the Day - May 28

A whip makes a cracking sound because its tip moves faster than the speed of sound.

Baseball - The Knuckleball

A knuckleball is a pitch thrown by a pitcher which does not spin and seemingly dances towards the plate. Its name comes from how it is thrown, with the knuckles instead of with the whole finger. It dances because with the "little rotation, asymmetric stitch configurations can be generated that lead to a large imbalance of forces and extraordinary excursions in trajectory." Since the ball is thrown with little velocity (usually a speed around 60-65 mph), the ball has more time to "dance" its way to the plate. Also, the fact that drag is actually more on a smooth ball rather than a rough ball (like a baseball), the ball has more of an opportunity to dance its way towards the batter. The problem that pitchers, catchers, and batters have (also its effectiveness), is that no one knows where it will possibly go. This results in many walks by the pitcher, passed balls (errors by the catcher), and horrible-looking swings by the batter.

Physics Fun Fact of the Day - May 27

When a solid body is totally or partially immersed in a liquid, it experiences an apparent loss of weight.

This is equal to the weight of the liquid displaced by the solid. This apparent loss of weight is due to the upward force exerted by the liquid on the solid. This upward force is called the force of buoyancy.