11-20

Physics Journal

It was a quiet morning on Thursday November twentieth, when disaster struck! Force problems proceeded to confuse the entire class, until Mr. Manning was incredibly annoyed because everyone was yelling for help. The students were given a paper called More Force Problems: Physics 1. I did not know there was a physics 2. At least in high school. The students were instructed to draw a free body diagram for every problem, and write both equations for the summation of F (crazy Greek letter F). The students worked on the paper for the rest of the period, and all was well. Except for those who were still confused.

The following is an example from the More Force Problems: Physics 1 worksheet. The source has requested to remain anonymous.

1. A tension force of 120N pulls an 8kg box with an acceleration of 7m/s^2 across a floor.

FBD: Mg = weight= 8 x 9.8 = 78.4

a) How much friction must be acting on the box? Fk = -64N Summation of F = ma = 8 x 7 = 56N Summation of F = Ft + (-Fk) 56N = 120 + (-Fk) 64 = -Fk Fk = -64 b) What is the coefficient of friction between the box and the floor? mewk = -.82 mewk = Fk/Fn = -64/78.4 = -.82

~ Sami Steele