Part A Draw a free-body diagram for the lower rod. The starting point, orientati

Question

Part A

Draw a free-body diagram for the lower rod.

The starting point, orientation, and length of your vectors will be graded.

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Part B

Draw a free-body diagram for the middle rod.

The starting point, orientation, and length of your vectors will be graded.

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Part C

Draw a free-body diagram for the upper rod.

The starting point, orientation, and length of your vectors will be graded.

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Part D

Find the weight of ball A.

Express your answer in newtons to three significant figures.

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Part E

Find the weight of ball B.

Express your answer in newtons to three significant figures.

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Part F

Find the weight of ball C.

Express your answer in newtons to three significant figures.

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Part G

Find the tension in S1.

Express your answer in newtons to three significant figures.

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Part H

Find the tension in S2.

Express your answer in newtons to three significant figures.

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Part I

Find the tension in S3.

Express your answer in newtons to three significant figures.

wA = N wB = N wC = N S1 = N S2 = N

Explanation / Answer

Use moment equation: Moment = Force * perpendicular distance

For a bar to stay horizontal moment in both directions has to be equal (moment is the force trying to spin the bar around an axis)

For your mobile, start at the bottom and work out weights as you go up. Ill do the bottom bar for you as an example.

6.8 N on left, A newtons on right. moments mean 6.8 * 4.2 = 8.8 * wA

wA = (6.8*4.2) /8.8 = 3.245N

and total weight on this bar S3=6.8 + wA =6.8 +3.245 = 10.04N

So tension on S3 = 10.04N (forces need to be equal or the bar would accelerate down)

similarly

10.04 N on right, B newtons on left. moments mean 10.04 * 5cm = 3.4 * wB

wB = (10.04*5) / 3.4 = 14.76N

and total weight on this bar S2 = 10.04 + wB =10.04 +14.76 = 24.80N

So tension on S2 = 24.80N (forces need to be equal or the bar would accelerate down)

24.80 N on left, C newtons on right. moments mean 24.80 * 2.3cm = 7 * wC

wC = (24.80 * 2.3cm) / 7 = 8.15N

and total weight on this bar S1 = 24.80 + wC =24.80 + 8.15 = 32.95N

So tension on S2 = 32.95N (forces need to be equal or the bar would accelerate down)

hope this helps

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