Name: ______Pd: _____

CMS STRONGMAN COMPETITION How Fast Can You Do Work?

Background Information: Work equals force times the distance through which the force acts. Force is expressed in Newtons (N) and distance is expressed in meters (m). Work is expressed in newton-meters, or the simplification, joules (J). The rate which work is done is called power. Power equals work divided by time. If work is in Joules (J) and time is in seconds (s), power is expressed in joules/second, or the simplification watt (W). James Watt was a British scientist who invented the steam engine. To find out how the power of his engine compared to that of a horse, Watt measured how fast an average horse could do work. He found the answer and expressed the amount of work performed per second as horsepower. One horsepower is the equivalent of 746 W.

Purpose: In this activity, we will experience the concepts of Work and Power using simple classroom materials. Please complete the following activity with a partner. You need to complete the data collection for both you AND your partner. If you are working in a group of 3, you must have YOUR data and one other person in your groups.

Pre-Lab Questions: 1. What has to happen in order for a force to do work on an object?

2. What is the formula for work?

3. What is the formula for power?

4. Do you do more work climbing the stairs quickly or climbing the stairs slowly?

5. Does it take more power to climb stairs quickly or climb stairs slowly?

1

How Fast Can You Do Work? Procedure: Calculate the work and power that you can do with different muscle groups.

ARMS 1. Measure the distance from the hanging mass to the top of the string. 2. Measure the time it takes you to raise the 0.9 kg (2 lb.) mass by rolling the string onto the dowel rod lifting the mass as you twist your hands. Record this time in the data table. 3. Repeat the procedure, only this time use the 1.3 kg (3 lb.) mass. 4. Record the mass of the object that was lifted. 5. Calculate the force by taking the mass (in kg) that was lifted times the acceleration due to gravity (9.8 m/s2). 6. Calculate the work and power that was produced from this activity and record your data in the table below. 7. Repeat the steps above for your lab partner.

Mass Distance Force Time Work Power ARMS (kg) (m) (N) (s) (J) (W) You –

Slow You –

Fast Partner –

Slow Partner –

Fast

LEGS 8. Determine the vertical distance in meters from the first floor to the second floor. To do this, measure the height of each step and count the number of steps between the first and second floor. 9. Measure how long it takes you to walk up the stairs at a slow pace. 10. Record your mass (kilograms) and time (seconds) the data table. 11. Determine the force used on the stairs by taking your mass (kg) times the acceleration due to gravity (9.8 m/s2). 12. Repeat the procedure but this time move at a faster pace. 13. Calculate the work and power that was produced from this activity and record your data in the table. 14. Repeat the steps above for your lab partner.

Mass Distance Force Time Work Power LEGS (kg) (m) (N) (s) (J) (W) You – Slow You –

Fast Partner –

Slow Partner –

Fast

CHEST 1. Choose a true pushup (on toes) or a simple one (on your knees). 2. Use the bathroom scale to determine the “force” that the arms must apply when doing a push-up. Record this value in the data table. 3. Measure the distance in meters that the top of your shoulder moves in one push-up (from straight arms to bent arms) = m 4. Measure the time it takes you to complete 5 push-ups. Record this in the data table. 5. Measure the time it takes you to complete 10 push-ups. Record this in the data table. 6. Repeat the steps above for your partner.

Distance Force Time Work Power CHEST (m) (N) (s) (J) (W) You – 5 push-ups You –

10 push-ups Partner –

5 push-ups Partner –

10 push-ups

ANALYSIS & CONCLUSION QUESTIONS: 1. Which activity required the most work for you? Explain this using the two variables that affect work.

2. Which activity produced the most power for you? Explain this using the two variables that affect power.

3. Was the power you exerted for each trial (slow vs. fast) on the stairs the same? Why or why not?

4. How did changing the mass (you vs. your partner) influence the work and power output while climbing the stairs?

5. Compare your power output in climbing the stairs quickly with the output of a horse by calculating your horsepower (the conversion is on the front of the lab).

6. How does your power output in climbing the stairs compare to the power output of a 100- watt light bulb?

7. If your power could have been harnessed and the energy converted to electricity, how many 100-w bulbs could you have kept burning during your climb?

8. Two people climb to the roof of a building. The old person walked up a gentle ramp, the young person climbed up a steep spiral staircase. Which person did more work? Explain.