Physics Blog 6

When I was on the computer last night, I accidentally hit my water bottle down.   The water got on my keyboard and mouse so I went to get a paper towel and absorb the water.  As I was doing this, I noticed that my hand and the water bottle created a sticky collision which moved the water bottle off the table.  Gravity then took control and tipped the bottle over and water spilled out.  Sticky collisions are m1v1+m2v2= (m1+m2)vf so we can find final velocity from our givens.  My hand was moving at around 4.2672 m / s and has a mass of about 1.81436948 kilograms.  The water bottle, which was half full had about 191.722284 grams or .191722284 kilograms. It's initial velocity was 0. Vf= (m1v1+m2v2)/ (m1+m2).  (1.81436948* 4.2672+.191722284*0) /2.00609176= 3.8593835 m/s. 

Physics Blog 5

Last night, I went to sleep at 1:30 because there was a marching band competition that lasted until 12:00.  So, when I woke up at 9:00 today, I was extremely tired (more tired than I usually am on a Sunday Morning).  Because I was so tired, when I walked down the stairs, I fell and went rolled the way down.  When I looked up at the stairs, I realized that gravity had done work on me.  Work equals force times distance and in this case work is equal to mass*gravity*height.  My weight is the force that that was acting upon me and makes gravity * mass while the I fell distance is equal to the height of the stairs.  Although the stairs makes an angle with the horizontal, the amount of work that is done is still the same as if I was just falling from a height of the highest stair.  My stairs are each 18 cm and there are 16 of them so the total height is .18*16m or 2.88 meters.  After I fell all the way down to the bottom floor, I found that Gravity did 55.6*9.8*2.88 joules or 1569 joules of work on me.  I did -1569 Joules of work because I did the same amount of work in the opposite direction.  And then I went back upstairs to sleep.