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Horsepower Lab

Background:

Power is the rate at which work is done. The English unit of work is the “horsepower (hp).” It equals 550 foot-pounds per second. The SI unit for power is the watt (W), which is equal to one joule per second. One horsepower is equal to about 746 watts.

1 W = 1 J/s

1 hp = 746 W

A 7.5 W motor is used to power small clocks. House lights use from 60 W to 100 W of power. A lawn mower usually has a 1300W engine. A 15000 W engine powered Henry Ford’s famous Model T, the most popular car from 1914 to 1927. Today, some 8-cylinder automobile engines generate over 190000 W of power. The world’s most powerful motors are used in heavy industrial machinery. These motors generate more than 74600000 W of power.

HOW POWERFUL ARE YOU?

SAFETY WARNING: Students with health problems should not perform the following activity.

Materials:

• Scale

• Meter Stick

• Calculator

• Only TWO students!

Procedure:

1. Record your weight in the Data & Observations Section 1 below.

2. Calculate how many Newtons of force this puts on the Earth.

3. Find a set of stairs where you can perform this lab. Because there are other classes going on at this time, be sure that you are responsible and respectful in the hallway.

4. Measure the height of one step and record the height in the Data & Observations Section 2 below. Fill in the rest of Section 2.

5. After you answer the questions, have one partner climb up the stairs. The other partner will time that person with a stopwatch. Record the time in Table 1. Repeat this 4 times.

6. Complete Table 1 WITH YOUR NUMBERS AND CALCULATIONS.

7. DO NOT COPY EACH OTHERS DATA! Repeat the lab procedure for your partner to obtain their own horsepower data. Every individual should have different numbers!!!

Data & Observations:

Section 1:

Your weight = _______________lbs

1 lb = 0.4536 kg your weight = ________________kg

How much force you put on the surface of the Earth = _________________N

Section 2:

Height of one stair = _______________________m

Number of stairs = _______________________

Total height of the stairs= _______________________m

What is the formula for Work?

Work =

What units are used to measure each variable?

How much work will you do to climb up those stairs? (Show your calculations below.)

What is the formula for Power?

Power =

Table 1:

|Trial |Work (J) |Time (s) |Power (W) |Power (hp) |

| | | |or (J/s) |1 hp = 746 W |

|1. | | | | |

|2. | | | | |

|3. | | | | |

|4. | | | | |

|Average | | | | |

Analysis Questions:

1. What does generate mean?

2. How much power did you generate?

3. How can you increase your power output?

4. How much power (maximum) do you think you can generate?

5. Have your partner time you one more time, so you test your hypothesis in #4. How much time did it take? What is the most power that you can generate?

6. How does your power compare to the power it takes to light a light bulb? How does your power compare to the power it takes to run a lawnmower?

7. How long do you think you could generate the average power that you calculated in Table 1?

8. If you ran up the stairs in half the time of another student of equal weight, how does the work that both of you do compare? How does the power you generate compare?

9. What if the height of the stairs was decreased and the depth of the stairs was increased. Would this change the work and power required to climb the stairs?

10. Read the background section again. What is the power of each of the objects described in the background section? Fill in the table below.

|Item |Power (W) |Power (kW) |Power (hp) |

| | |1kW=1000W | |

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