Unit 8 - Work and Power

1. Work done is measured in which of the following units?

• Newton

• Watt

• Kilogram

• Joule

1. Power is measured in which of the following units?

• Newton

• Watt

• Kilogram

• Joule

How many watts are there in a kilowatt?

• 10 W

• 100 W

• 1000 W

• 10000 W

How many watts are there in a megawatt?

• 1,000 W

• 10,000 W

• 100,000 W

• 1,000,000 W

One horsepower is the power output of one horse when it lifts a mass of 33 000 lb of water through a height of one foot in one minute as shown in the image.

You need to know that 1 lb = 0.453592 kg and one foot = 0.3048 meters.

Calculate the mass of water the horse lifts in one minute.

• 1.497 x 10^3 kg

• 1.497 x 10^4 kg

• 1.497 x 10^5 kg

• 1.497 x 10^6 kg

One horsepower is the power output of one horse when it lifts a mass of 33 000 lb of water through a height of one foot in one minute as shown in the image.

You need to know that 1 lb = 0.453592 kg and one foot = 0.3048 meters.

Calculate the weight of water the horse lifts in one minute. (Assume that g = 10 N/kg)

• 1.497 x 10^3 N

• 1.497 x 10^4 N

• 1.497 x 10^5 N

• 1.497 x 10^6 N

One horsepower is the power output of one horse when it lifts a mass of 33 000 lb of water through a height of one foot in one minute as shown in the image.

You need to know that 1 lb = 0.453592 kg and one foot = 0.3048 meters.

Calculate the work the horse does in one minute.

• 4.56 x 10^3 J

• 4.56 x 10^4 J

• 4.56 x 10^5 J

• 4.56 x 10^6 J

One horsepower is the power output of one horse when it lifts a mass of 33 000 lb of water through a height of one foot in one minute as shown in the image.

You need to know that 1 lb = 0.453592 kg and one foot = 0.3048 meters.

Calculate the power output of the horse.

• 380 W

• 3800 W

• 760 W

• 7600 W

An average man needs to eat food containing about 2500 kcal of chemical potential energy per day (1 kcal = 4.18 kJ). a

What is 2500 kcal expressed in joules?

• 5,225,000 J

• 10,450,000 J

• 10.45 MJ

• 13.85 MJ

An average man needs to eat food containing about 2500 kcal of chemical potential energy per day (1 kcal = 4.18 kJ). a

Calculate the power output of the average man, even when he is doing no work.

• 60W

• 12.1 W

• 242 W

• 121 W