- #1
brendan3eb
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Homework Statement
A uniform sphere of mass m and radius r is held in place by a massless rope attached to a frictionless wall a distance L above the center of the sphere. Find (a) the tension in the rope and (b) the force on the sphere from the wall.
Homework Equations
net torque = 0
net force = 0
t=force of tension
F=force of wall
mg=gravitational force on ball
The Attempt at a Solution
well, strangely enough I am able to solve for part B. choosing the point where the string is attached to the wall as my origin. I am able to determine the torque caused by tension to be 0 as the tension force runs 180 parallel the string. Using motion arm times force = torque, I can find the remaining torques so that:
-mgr+t*0+L*F=0
which yields
F=mgr/L
which is the correct answer to part B. However, I have no clue how to solve part A. I have already used my torque, so I tried setting the force equations for the x and y-axis to 0.
T*cos(x)-mg=0
F-T*sin(x)=0
but that doesn't get me anything close to the correct answer of
T=(mg/L)*sqrt(L^2+r^2)
help please