# physics

A 0.33- kg pendulum bob is attached to a string 1.2 m long and hangs vertically as shown in Figure 1. What is the change in the pendulum bob’s gravitational potential energy as it swings from the lowest point of the pendulum to a point that is 35 degree to the vertical?

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1. Figure from the geometry the change in vertical height.

PE=mgh

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bobpursley
2. can you give the solution?

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3. Yes, I could.

I will be happy to check your work, but you need to do your own thinking. Answer grazers learn nothing.

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bobpursley
4. p=mgh
p=.33*9.8*(1.2-1.2*cos35)
P=70.2M

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5. Are you sure ?

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6. Draw the picture and do some geometry. 1.2m can be put on the other side of the triangle. The lower portion of the B ball we will call h. Cos(theta) = y / 1.2m ---> y = cos(theta) x 1.2m. (y is the length from the tip till the part what h is). Gotta do some algebra to get the acutal length of h, which I'm sure you can do yourself. You can then solve PE from there with the Potential Energy Formula. PE = mgh

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