[The Fifth Blog] Momentum.

       Yesterday I attended the UH versus New Mexico State football game – my first live UH football game, might I add, and only my second time sitting in Aloha Stadium.  Honestly, the (unnecessarily) loud, screaming fans and blinding bright lights don’t do much for me, but that’s okay because at least I got to experience some physics while I was there. 

I didn’t take any pictures of my own, but this one will do:

       I will refer to the UH player as A, the other as B, and assume that they were running toward each other from opposite directions prior to the collision.  The collision that these two players experienced was a perfectly inelastic collision, so momentum was conserved but kinetic energy was not, and the two players ended up “stuck together” (Hmm, what if it had been an ordinary inelastic collision and they had bounced off of each other instead... o_O). Anyway...if we give the two players random masses and initial velocities... (A has a mass of 110 kg and was moving at a velocity of 5 m/s and B has a mass of 90 kg and was moving at a velocity of -5 m/s) we can solve for the common final velocity of the two players upon impact because we know that momentum is conserved. 

                                                                            

                                                                             

[The Fourth Blog] Work, Energy, & Power.

When we hear the word work, we usually think of that place where our parents go while we're in school or, much more likely (being that we are such studious 'Iolani students), homework. To a physicist, though, work can be defined as displacement times force in the direction of displacement (W = FcosθΔx) or as a change in energy (W = E_f - E_i).

     I normally don't think much about walking up the stairs at home because it's something I do every day, but I thought twice about it today since such an action can be related to physics.  When I am standing at the bottom of the stairs, kinetic and potential energy are both zero (no velocity and no h). When I reach the top, though, both my kinetic and potential energy have changed and thus I have done work - little as it may be. To calculate my work, I find my total energy at the bottom (0 J) and subtract it from my total energy at the top (612 J), resulting in 612 J of work. Not much work, but work nonetheless...  (And probably a greater value than that representing the amount of homework I have accomplished thus far. Not good.) From this I can calculate my power (P = W/t), which comes out to be 266 W (or 0.357 hp).  Physics has redefined the meaning of work for me and has taught me about the relationship between work, energy, and power.   

         

I made it to the top. :]