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Half a coconut of mass $0.25$ kg is suspended from a tree branch by a light piece of string of fixed length $0.4$ m. A gust of wind displaces the bob from its equilibrium position and the center of mass of the coconut rises $20$ cm above its rest position.

a) What is the potential energy as it reaches its maximum height?

b) What is the kinetic energy of the coconut at its maximum height and when it passes through the equilibrium position?

c) What is the maximum speed of the coconut?

d) What is the maximum tension of the string?

Can someone please help me with these questions? I am desperate...

Vinyl_cape_jawa
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s20081063
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    You should at least add mathematical definitions of the relevant terms (potential energy, kinetic energy, etc.) if you want to recast this as a math question. This might be better suited for physics.stackexchange.com. –  Nov 09 '17 at 18:52
  • Please also include your attempt at the problem – A. Goodier Nov 09 '17 at 19:04
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    "I know this is more physics than math.." Then why ARE you posting it here? Okay, to answer your questions as a mathematician. a) I don't know what "potential energy" is. b) I don't know "kinetic energy" is. I know that height is the equilibrium position + 20cm. Does that help? c) Nothing in the problem mentions time so with information given in the problem and my knowledge of physics, this in unanswerable d) I don't know what tension is. Was any of that helpful? Maybe you should define your terms and list any known equations. – fleablood Nov 09 '17 at 19:16

1 Answers1

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a) potential energy $= mgh$

b) energy is conserved.

c) since energy is conserved... $\frac 12 mv^2 + mgh$ is constant.

d) This is the trickiest part, cicular motion requires centripetal acceleration = $\frac {v^2}{r}$ this is added to the tension on the string from gravity.

I suppose for part d) you might also consider the tension on the string before the system is set into motion.

Doug M
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