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Topic: Box on frictionless incline. Force Problem.  (Read 3527 times)

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Offline MrHappy0

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Box on frictionless incline. Force Problem.
« on: October 01, 2011, 12:12:06 AM »
A woman pushes horizontally on a wooden box of mass 82.8 kg sitting on a frictionless ramp inclined at an angle of 27.0o. Assume that the box is at rest or in uniform motion along the ramp.
Calculate the magnitude of the force (in Newtons) exerted by the woman on the box.

So I know how to solve this problem if the lady was pushing on the wooden box with force parallel to the ramp incline. I messed around with the x-axis being parallel to the plane and I tried it parallel to the horizontal force. Both of these ended in dead ends. Any pointers?


Here was my attempt. It is wrong though. I believe my idea of Fnet=Force-Weight=ma=zero is correct if you put the x-axis parallel to the ramp but my Trigonometry might the source of error. 

Fnet, along x= FlLady-Boxcos[theta]-mgsin[theta]=0 ---> Flady-box=mgsin[theta]/cos[theta]

Offline fledarmus

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Re: Box on frictionless incline. Force Problem.
« Reply #1 on: October 03, 2011, 08:28:25 AM »
If the plane is parallel to the ground, the force of gravity acting on the box would be perpindicular to the plane. No force would be required to keep the box from moving in a direction parallel to the plane.

If the plane is at an angle to the ground, how much of the force of gravity acting on the box would be in a direction parallel to the plane? That is the amount of force that you would have to apply to the box to keep it from sliding down the plane.

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