- #1
joe_coolish
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Homework Statement
A ball (mass m = 250 g) on the end of an ideal string is moving in circular motion as a conical pendulum as in the figure. The length L of the string is 1.85 m and the angle with the vertical is 37°.
- What is the magnitude of the torque exerted on the ball about the support point (Nm)?
- What is the magnitude of the angular momentum of the ball about the support point (Kg m^2/s^2)?
- What is the direction of the angular momentum of the ball about the support point?
Homework Equations
t= r x F
t= rFsinθ
L= r x p
p= mv
v= 2PI * r * r/period
period= 2PI*SQRT(h/g)
T=mg/cosθ
The Attempt at a Solution
1) My first attempt at finding the torque was to find the the tension of the string (T) which equalled:
T=3.0677
I figured that T is the only force acting on support point so I took T and plugged it into
t= rFsinθ
and got 2.055. The correct answer was 2.73. After playing with the numbers, switching sin with cos got me the correct answer
t= rFcosθ = 2.7277
I don't know if that is coincidence or what. Is that correct?
2) I took F and replaced it with p and got 0.637. The correct answer was 1.33, which is why I think that the formula to get the answer for 1) was just coincidence. I'm not too sure where to go here.
3) I have no idea!