25- Sept. - 2014 Work and Power Activity

Work and Power Activity

Objective:

 Calculate the work and power for each task and compare results of each.

Set- up (2 of them):

 1) Walk a flight of stairs and time yourself until you reach the top and for the second trial you run. We measured the height of one step and counted steps to get an approximate height as seen in (fig 1).

2) With a long rope, weighted bag with a given mass and a plant with a pulley on the top of the balcony with the same height, time how long it takes to hoist the bag to that height as seen in (fig 3).

Figure 1. Classmates measuring the steps while one is timing
 themselves on the stairs. Set-up for task 2 in background

Part 1:

 Following the procedures in Set up 1, we found the following:

Height of one step= 17cm 

# of steps= 26

h= (26)*(17cm)(1m) = 4.42m 

(100 cm)                    

I. Walk time: 14.2s 

II.  Run time: 8.3 s 

 My weight (w)= 377.91 N 

Below in (fig 2.) is the calculations to find the work and Power for each Trail (I. and II.) in this task.

Figure 2. Calculations using what was known and what was recorded in the trials.
Notice Work is the same for both but Power varies depending how fast we did the work.

Part 2:

 In this task, we had to perform the set up 2 procedures. We have found the following:

Figure 3. Me starting my task to hoist the bag.

h= 4.42 m

mass of weighted bag= 6 kg

Lift time: 16.14 s 

Below in (fig 2) is the calculations to find the Work and Power for the task.

Figure 4. The calculations using what is known and what was recorded in the trial.
Once again, no matter how many trials I do, as long as change in height h is the same,
 work will be the same but Power will vary.

 Conclusion:
 Through observation and calculations, if the force applied and distance of a task are constant (in respect to h) then no matter how fast one may perform it, the Work is the same. However, Power is purely dependent on time. So even with the same amount of work in numerous trials, Power will vary as shown in Task 1. Task 2 has also shown that if an individual's weight was being hoisted the same height as the stairs, the work in both tasks would be the same.