
#1
Dec1811, 04:53 PM

P: 6

1. The problem statement, all variables and given/known data
A ball of mass 0.23 kg is attached securely to a string, then whirled at a constant speed in a vertical radius of 0.75 m. Calculate the minimum speed of the ball at the top of the path if it is to follow a complete circle. 2. Relevant equations F = mv(squared)/R 3. The attempt at a solution I first solved for Fc when the ball is at the top of the circle with F=mv(squared)/R  mg and it equals 1.7 N. I then rearranged the equation to solve for V using V = the square root of FR/m and got the answer 2.35 m/s. My sheet says the answer is 2.7, which is pretty close to what I got, but I may have done something wrong. Any thoughts? 



#2
Dec1811, 05:16 PM

P: 46

This is what i think, right so the forces acting on the mass are gravity and the tension of the string, it's best to draw a diagram.
T = tension. Defining positive direction to be downwards. At the top of the circle: F = mg + T As you say F= (mv^2)/r for circular motion. So equate these. Now can you figure out how to find the minimum speed? 



#3
Dec1811, 05:51 PM

P: 6

Yes, I've figured it out now, thanks!



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