September 29 2014 - Finding the Power used out of class

Purpose: To find the power required to go up a staircase and to pull a backpack up to a certain height by using a pulley.

This is the staircase that we used to time how long it took us to go up. We had to times, one for going up slow and one for going up fast.

This is the system with the pulley and the backpack. We used the 9 kg backpack system.

First we are going to calculate the time needed to go up the staircase in two scenarios, one going up slow and the other going up fast. Then, we are going to calculate the height of each step and count how many steps are in the staircase, so we can find the total height. After done with that, we are going to go to the backpack system, where each one of us is going to pull the cable holding the backpack and we are going to time how long it take us. The height pulled will be the same as the staircase.

 These are the calculations used to find the height of the staircase which is 3.74 m, the gravitational potential energy of going up the staircase which is 1832.6 J, and the power used in each execution, one slow and one fast.

This is the calculation to find the power used in pulling the backpack up to the top of the staircase, the power that I used was 21.7 Watts.

Summary: After we calculated the time for each execution and height of the staircase, I found the work(mgh) of me going up to be 1832.6 J. Dividing my work by the time of each execution(slow=15 seconds, fast=8.9 seconds), I found out that I used a power of 122.17 Watts when going slow, and 205.9 Watts when going fast. After that, we timed how long it took us to pull the 9 kg backpack. I found the work in that backpack going up to be 329.87 J. Again, by dividing the work by the time it took me to pull up (15.2 seconds), I found that the power required to pull the backpack was 21.7 Watts.