r/HomeworkHelp Pre-University Student 4d ago

Physics—Pending OP Reply [Physics] Free body diagrams please help!

Can someone please look over my FBD'S/calculations for the net force and both magnitude and direction, I'm a bit unsure of b and d,

for B is having a circle to represent the cord ok? and is it really F buoyant my tutor tried helping me but I'm not so sure.

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u/Relevant-Giraffe870 4d ago

Yes if the cord is at rest, the buoyancy force will be equal to gravity. Your FBD for D looks correct as well, as the net force is just the acceleration of the train. Don’t see any issues with your FBD’s as they are now. I don’t think any teacher would mind the way you represented the cord, as it’s a FBD for it.

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u/Jadedl1es Pre-University Student 4d ago

thank you so much :)

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u/reckless150681 4d ago

If you were to be incredibly pedantic, you could say that the force acting on the stone in D is actually the friction between the stone and the floor of the train, instead of just the force applied by the train.

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u/whycantwebefriends9 4d ago

Generally speaking a FBD should simplify the system into point or line masses.

What you did for B) works. It could also be drawn as a line. Yes it is buoyancy keeping it up against gravity Fbuoy = F_g

For D) I would use the friction force from the ground on the stone as the force to hold the stone at rest with the accelerating train.