Yesterday, (October 16, 2010) I watched the the Hawaii VS. Nevada football game.  After watching the play replay of the  Nevada player, Mike Ball, make a 84-yard kickoff return, I noticed that when the first diving tackle missed by a Hawaii player, the player slid about 2 meters before coming to a rest.  This is due to friction.  When the football player dove, he had an initial velocity and was like a projectile.  However, after he hit the ground, he slid across the ground before stopping.  After watching this, I decided to try and the find mu of his jersey to the AstroTurf.  We can find the mu.  Because he was sprinting before he dove, his initial velocity was around 7 m/s.  If he slid 3 meters on the ground then we know his acceleration is- 8.2 m/s^2 because 7^2=2(a)3. If his weight was 200 pounds, then his normal force would also be around 200 pounds.  200 pounds is equal to about 890 newtons and this means his mass is 81.6 (890/9.8 = 81.6 kg).  a=Net Force/ mass.  Net Force = 81.6*-8.2=-670N.  Friction = 670N.  890*mu = 670N and therefore mu is 0.75.

Blog 3

On Friday, October 3 2010, my physics teacher, Mrs. Chen had a substitute by another physics teacher, Doc. For a real life example of the lesson, he made the whole class ride the elevator. As we went up to the third floor from the first, we could feel our bodies getting heavier for the first few seconds. Later during the ride, we felt normal, and finally after that we felt lighter. These changes that we experienced are caused by the change in our normal force. When we are just standing, we have two forces acting upon us: normal force and our weight. Normal force is the force that negates the force of gravity. On the elevator, our normal forces rose and stayed constant for a while before decreasing back to a halt. The normal force affected our net force and our net force changed our acceleration. As we accelerated upwards, our normal force rose making us feel heavier. When the acceleration became 0, our normal force also became 0. When we slowed down before reaching the fourth floor, we felt lighter because our normal force decreased. We also felt this as we went back to the first floor but in the opposite order. The same thing can be said about a scale. When I push down on the scale, the scale reads higher but when I don't push down as much then the scale reads lower. The scale is reading the normal force. I can't fix this font...

 With less normal force.

 With more normal force.

. 

Normal Normal Force.