Physics Unit 8 (Part 2)

Today we learned all about power. Power, is the rate at which work is done, and work, in case any of you have forgotten, is the change in energy. To find power, you take an objects work and divide it by the amount of time used. The unit used to measure power is watts.

Power = work ÷ time
Work = newtons x meters

We had a lab today where we had two students run up stairs. We then recorded their masses, the distance up the stairs they travelled and the amount of time it took them to get up all the stairs. With that information, we were able to find the students' forces, which then allowed us to find their work as well as their power.

In the picture to the left, my dog is running down some stairs. Let's say she has a mass of 8kg, ran down 1 meter of stairs which took her 2 seconds, and that she's on Earth (which she is), so gravity would be 9.8ms^2. This means that she had a force of 78.4N (force = ma). Now that we have her force, we can find her work, which would be 78.4J (work = Nm). Finally, we can find her power, which would be 39.2W (power = work/time). If Abby was a Great Dane, she would have a much higher power, because when object's have greater masses, they have greater powers.



We also learned how to draw energy graphes, which is actually really confusing at times. The graphs, no matter how confusing they are, are actually really good at demonstrating the concept of potential energy vs. kinetic energy. Through time, as the potential energy went down, the kinetic energy got higher, which was made clear in the graphs. The same thing works for other concepts too, like kinetic energy vs. work.