- #1
miglo
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Homework Statement
To move a large crate across a rough floor, you push on it with a force F at an angle of 21° below the horizontal, as shown in the figure. Find the force necessary to start the crate moving, given that the mass of the crate is m = 37 kg and the coefficient of static friction between the crate and the floor is 0.60.
Homework Equations
F_x=F\cos{\theta}
F_y=F\sin{\theta}
F=ma
W=mg
f_s=\mu_sN
The Attempt at a Solution
so i know that \sum{\vec{F_x}}=F\cos{\theta}-\mu_sN=0
and \sum{\vec{F_y}}=N-F\sin{\theta}-mg=0
solving for N i get N=F\sin{\theta}+mg and plugging this in for N in the sum of the forces in the x direction i get F\cos{\theta}-\mu_s(F\sin{\theta}+mg)=0 and finally solving for F i get F=\frac{\mu_smg}{\cos{\theta}-\mu_s\sin{\theta}}
so i plugged in all the values given and yet i still got the wrong answer (my homework is online and i get 5 tries for each question)
my guess is that I am using the wrong angle, should it be 21? or 360-21=339?
or did i not solve for F correctly?
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