Help with potential energy and energy conservation please! Problem 7.78 Part A A

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Help with potential energy and energy conservation please!

Problem 7.78 Part A A small block with mass 0.0425 kg slides in a vertical circle of radius 0.550 m on the inside of a circular track. During one of the revolutions of the block, when the block is at the bottom of its path, point A, the magnitude of the normal force exerted on the block by the track has magnitude 4.00 N. In this same revolution, when the block reaches the top of its path, point B, the magnitude of the normal force exerted on the block has magnitude 0.675 N How much work was done on the block by friction during the motion of the block from point A to point B? Express your answer with the appropriate units. friction Submit My Answers Give Up

Explanation / Answer

7.78) Net centrifugal force on the block at lower point= 4-mg=4-0.0425(9.8)=3.58 N

mv^2/r=3.58

0.0425v^2/0.55=3.58

v=6.81 m/s

Net centrifugal force at the top=0.675+mg=0.675+0.0425(9.8)=1.09 N

mvt^2/r=1.09

0.0425vt^2/0.55=1.09

v=3.75 m/s

Conserving energy,

1/2mv^2=1/2 mvt^2 +f+mg2r

Here, f is the work done by the friction

1/2(0.0425)(6.81)^2=1/2(0.0425)(3.75)^2+f+0.0425(9.8)(2*0.55)

0.99=0.30+f+0.46

f=0.23 J

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