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nightshade123

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**[SOLVED] potential energy and turning points**

## Homework Statement

A block slides on the frictionless loop the lopp track shown in this img, what is the min height at which it can start from rest and still make it around the loop

## The Attempt at a Solution

I haev solved this problem TWO ways, and i can't decide which way is correct

the eqn...

**U0+K0 = K+U**

where U = potential energy and K = kinetic energy

first

**m * g * h + (1/2) * m * v^2 >= m * g * 2 * R**

final answer =

**h = 2R**

the other way is

**m * g * h >= (1/2) * m * v^2 + m * g * 2 * R**

final answer is

**h = (5*R) / 2**??

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