Work and Power Lab

5.1.1: Measuring Work:

1. Because work involves the force over a distance, so the force, which is the weight of a person, depends on a person's mass. Also, work is directly proportional to force; therefore, a person weight twice as much as his friend will do twice the work.
2. If you travel along the distance from the bottom step to the top step, you are doing no work on it because you are not moving it against the force of gravity.
3. Work is the change of kinetic energy, whereas impulse is the change of momentum.
4. The work of lifting a 2000-N object a vertical distance of 10m would be equal the work of lifting a 1000-N object a vertical distance of 20m.
6. The work does not depend on time because work is defined as the product of force over a distance, which do not involve time.
7. In half revolution, the wheel travel a distance of half the circumference (pi). Work is 31.41 J.
In a complete revolution, the wheel travel a distance of 2pi(r). Work is 62.83 J.

5.1.2: Measuring Power:

1. As a person runs up the ramp in half the time of another person of equal weight, he does the same work but uses twice the power because work does not involve time while power is the work over a time period. Half of the time will cause the power to double because they have inversely proportional relationship.
2. As the vertical height of the stair is reduced by half, the work will be half of its original work. Thus, power will be reduced by half. (work and power are directly proportional).
3. It is not necessary to use greater power to perform such fears because the power indicates the work over a time period.
4. 1 hp = 745.7 Watts. The work done is (745.7W)(60s) = 44742 J. Gallons of water: 1182 gallons.
5. Power in horsepower of a 100-watt light bulb: 0.134 HP
Power in kilowatts of a 200-horsepower engine: 149.14 kW.

5.1.3: Reading Your Electric Meter:

1. 5003kWh - 3866kWh = 1137 kWh
2.

3. Because we keep consuming energy, graph of household energy consumption varies from day to day.

4. 5793kWh - 5459kWh = 334kWh. It costs $24.34.

5.1.4: Conserving Electricity

1. Unit of electric energy is kWh, while unit of electric power is W

2. I will use more energy than my friend ( 50kWh > 40kWh)

3. Power accounts for the great difference in consumption energy.

4. 1450 MW = 1450 x 10^6 W = 1450000 kW