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NamikazeBurst
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Homework Statement
Okay, so I am given an acceleration that I need to accelerate a box-thingy, along with a weight inside. Friction is included. I need to come up with a mass that is connected through a pulley to the box. This mass has to accelerate the box at the given acceleration.
I am not asking for the exact mass I need for my need acceleration. I just want to know how to get that mass.
Homework Equations
Fnet = ma
##F_g = m_g##
##F_n = F_g##
The Attempt at a Solution
I am having trouble figuring out what mass I need. I know the 'driving force' is ##F_g## (mass I need * 9.8). The resisting forces I believe are the ##F_g## of the box (box total mass * 9.8) and the friction force (I am told I don't need the coefficient).
To get the friction force, I pulled the box with a Newton Spring Scale, and subtracted the net force I want (F=ma) from the pulling force. My equation for acceleration ended up being:
a = (mBg - mAg - Ff) / mT
Where the mBg is the force from the unknown mass, mAg is the force of gravity on the box, Ff is the friction force, and mT is total mass of the system.
Plugging my numbers in after rearranging for mB, I ended up getting a small mass (~0.5kg), and I do not believe that would accelerate the box to the rate I need.
What did I do wrong? Is the one force (Fg of box) supposed to be mAgsinθ (where θ = 0 degrees)? Was the friction force wrong? Did I completely mess up? Please help, and thanks!
Diagram for reference:
Diagram
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