DATE:
8/19/2019
Class
Name
Student number
TWALA TS
217011428
SWIEGELING BJ
218012050
HLABA NE
218000442
MOCHOCHOKO KA
218011013
KOENA GK
218011878
BOLEKE ML
218012227
SUBJECT:
PHYSICS PRACTICALS
PRACTICAL:
Your Personal Power Rating
EVALUATION SUMMARY:
PREPARATION FOR PRACTICAL:
1. Aim of the Practical
5%
2. Summary of Theory
10%
3. Experimental Procedure
10%
COMPLETING REPORT:
4. Sketch of the Apparatus
10%
5. Experimental Data
15%
6. Calculations
35%
7.. Conclusion
10%
8. Accuracy, Neatness, Language
5%
Total:
100%
AIM:
To measure personal power rating for climbing stairs
THEORY:
Typically, people have different power ratings for different tasks. When someone climbs
the stairs, energy is transferred from the chemical store of energy in their muscles (food
and oxygen) to increase their gravitational potential energy.
Gravitational potential energy = mgh = work done in climbing the stairs
Where mg is the weight of the climber and h is the vertical distance climbed.
Quickly lifting the vehicle to a fixed height does require more power, however. Power is
defined as work done per unit time. By lifting the vehicle quickly, you have done the
same amount of work, but in a shorter time.
EXPERIMENTAL PROCEDURE:
1.
All group members weighed themselves on the bathroom scales and the results
were recorded.
2.
A flight of stairs was found at the Ampi-theatre.
3.
The total height of stairs was measured and entered below.
4.
Each member of the group ran up the stairs, whilst the other member timed them
standing at the top of the stairs.
5.
It was ensured that all group members participated in the activity.
APPARATUS:
•Bathroom scale
•Tape measure, 5 m
•Stopwatch
•Yourself
EXPERIMENTAL DATA:
Data Table
Group member
Weight (N)
Time (s)
Work done (J)
Power rating
(J/s)
Mochochoko AK
686
12.60
388.30
54.44
Koena GK
588
13.30
332.83
44.21
Twala TS
980
12.39
554.71
79.10
Swiegeling BJ
656.6
10.59
371.66
62
Hlaba NE
637
11.00
360.56
57.10
Boleke ML
666.4
13.50
377.21
49.36
Average
702.33
12.23
397.55
56.72
Total height of stairs
0.6536m
CALCULATIONS:
W=mg
1.The work each group member did in climbing the stairs
W= F∆x cosꝋ
=(686)(0.6536m)cos30⁰
=388.30 J
W= F∆x cosꝋ
=(588)(0.6536m)cos30⁰
=332.86 J
W= F∆x cosꝋ
=(980)(0.6536m)cos30⁰
=554.71 J
W= F∆x cosꝋ
=(656.6)(0.6536m)cos30⁰
=371.66 J
W= F∆x cosꝋ
=(637)(0.6536m)cos30⁰
=366.56 J
W= F∆x cosꝋ
=(666.4)(0.6536m)cos30⁰
=377.21 J
Average work done
(388.30+332.86+554.71+371.66 +366.56+377.21)
= 2385.3
2385.3/6
=397.55 j
2.The power rating of each group member
P= W/∆t
=686/12.60
=54.44W
P= W/∆t
=588/13.30
=44.21W
P= W/∆t
=980/12.39
=79.2W
P= W/∆t
=656.6/10.59
=62W
P= W/∆t
=637/11
=57.10W
P= W/∆t
=666.4/13.50
=49.36W
Average power rating
54.44W+44.21W+79.2W+62W+57.10W+49.36W
=346.31W
346.31/6
=56.72W
3. A typical human’s power rating for an entire day is 100watts (W = J/s). How did your
power rating when climbing stairs compare to that value?
The power rating is about half the given value showing more work is done
4. A typical human consumes 2500 Kcal of energy during a day. This is the equivalent
to 10,450,000 J! Say you decided to run stairs all day. How much energy, in Joules,
would you burn in climbing stairs all day?
10450000x24x60x60
=9.0288x1011 J.s
5. How many Kcal of food energy would you need to consume to do so? (Remember
that there are 4180 J / Kcal.)
9.0288x1011 x4180
=3.771012 KJ
CONCLUSION
The group determined the output of power when a person climb the stairs. We studied
the human power output and key points of the work done. In our case after we
calculated power rating, it can be assumed that a person must apply at least
702.33N(Group average) downwards force up on the stairs to elevate the body. It can
also be assumed that the angle between the force of stairs on a person and person’s
displacement is 0 degrees.
The other part to consider would be the timer error. During the experiment the group
determined the power output when each group member in the group climbed the stairs
while the other was recording their time. Each group member had different power rating,
and this was because of experimental errors which involved inaccurate timing made by
the person who was using the stopwatch, other group members were skipping some
stairs while climbing and within the group people had different weights which might also
be the cause of getting different power rating.
The rate of power has been studied. The relationship between work done, time and
power has been observed. After performing this experiment, we have understood the
rate of power and the relationship between work done and time.