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If energy is movement, how come I get tired just from holding a heavy object? (multiverse.soulism.net)
submitted 1 month ago by to c/nostupidquestions@lemmy.ca
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In high school physics, I learned that the equation for energy from moving something is a factor of force and displacement. So if an object remains stationary, then no matter how much force is put into it, no energy is expended.

So how come if I hold a heavy box filled with dumbbells, I get tired? I'm obviously putting a lot of newtons into it to keep it from falling, but it's not moving. So how is the weight of the object causing Me to expend energy?

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[โ€“] 3 points 1 month ago (2 children)

Look at energy = force, not only movement (one type of force, kinetic force). There are other types of forces, like gravity. In your example, you're constantly providing a counter-force to gravity.

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  • [โ€“] [S] 3 points 1 month ago (1 child)

    But energy isn't force. Energy is force times distance. There's no distance.

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  • [โ€“] 1 point 1 month ago

    The distance is to the ground (technically to the centre of the nearest gravity well, but generally the ground gets in the way of that). The box would move towards the ground in order to expend potential kinetic energy and reach a lower energy state, but the counter force you're providing cancels it out, keeping it in place.

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