Physics Chapter 2

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mcat5122018
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Joined: Sat Mar 03, 2018 3:33 pm

Physics Chapter 2

Post by mcat5122018 » Sun Apr 15, 2018 11:50 pm

Hi,

In chapter 2 of the physics book, I was reading about mechanical advantage. I did not fully understand the concept based on the figures that were shown. Can you please explain them to me? I have attached the two figures used in the book to explain the concept.

In regards to power: If I understood it correctly, a system that does work and releases energy quickly has more power vs a system that takes time to do work and release energy. The book talks about firewood vs TNT and the amount of energy both have. It said that although TNT has less energy, it has more power because of its instant release whereas firewood has more energy, but is less powerful because it's released slowly. Therefore, in my mind, I thought of it like this: less energy, instant release, more power. However, could this be true as well: more energy, instant release, more power?

Thank you.
Attachments
Mechanical Advantage Ramp.png
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Mechanical Advantage Seesaw.png
(137.64 KiB) Not downloaded yet
NS_Tutor_Andrew
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Posts: 520
Joined: Mon May 23, 2016 1:47 pm

Re: Physics Chapter 2

Post by NS_Tutor_Andrew » Tue Apr 17, 2018 1:35 pm

Hi mcat5122018,

Re: mechanical advantage, the key idea is that you can use less force to do the same amount of work. For the example that you uploaded, the idea is that since W = F*d, you can decrease F and do the same amount of work if you increase d to compensate. The calculations in that figure are an example of how you can verify that this is indeed true.

Re: power, you're right. Since P = W/t, you could increase power by keeping W constant and decreasing t, or by keeping t constant and increasing W. You could also both increase W and decrease t, which would strongly increase power (that seems to be the scenario you're referring to). So yes, absolutely! Usually the MCAT only tests the effects of changing one variable at a time, though, but potentially both could be manipulated.
Andrew D.
Content Manager, Next Step Test Prep.
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