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# A-level physics question on power.

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1. This was a question from a Unit 1 physics paper. I reaaaallly don't understand how we'd attempt this!!!

In the eighteenth century, James Watt manufactured steam engines. He needed a way to demonstrate the benefits of these compared to the horses they replaced. He did some calculations based on horses walking in circles to turn a mill wheel. Watt observed that a horse could turn the wheel 144 times in one hour. The horse travelled in a circle of radius 3.7 m and exerted a force of 800 N. Show that the work done by the horse in turning the wheel through one revolution was about 20 000 J.
2. (Original post by slaya)
This was a question from a Unit 1 physics paper. I reaaaallly don't understand how we'd attempt this!!!

In the eighteenth century, James Watt manufactured steam engines. He needed a way to demonstrate the benefits of these compared to the horses they replaced. He did some calculations based on horses walking in circles to turn a mill wheel. Watt observed that a horse could turn the wheel 144 times in one hour. The horse travelled in a circle of radius 3.7 m and exerted a force of 800 N. Show that the work done by the horse in turning the wheel through one revolution was about 20 000 J.
Well work done is force times distance and in this case that is 800 times 2 X pi X 3.7 Joules per revolution
3. (Original post by slaya)
This was a question from a Unit 1 physics paper. I reaaaallly don't understand how we'd attempt this!!!

In the eighteenth century, James Watt manufactured steam engines. He needed a way to demonstrate the benefits of these compared to the horses they replaced. He did some calculations based on horses walking in circles to turn a mill wheel. Watt observed that a horse could turn the wheel 144 times in one hour. The horse travelled in a circle of radius 3.7 m and exerted a force of 800 N. Show that the work done by the horse in turning the wheel through one revolution was about 20 000 J.
Overall workdone=force x distance. The force is 800N. so to calculate the distance the horse goes around a circle, therefore the perimeter of the circle is 2pi x radius. That gives you the distance travelled. therefore when you calculate it out you get an answer of 18598.22851J

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