Problem 12.71 A 70.0-kg painter is on a uniform 21-kg scaffold supported from ab

Question

Problem 12.71

A 70.0-kg painter is on a uniform 21-kg scaffold supported from above by ropes. There is a 3.3-kg pail of paint to one side, as shown (Figure 1) .

Part A

Can the painter walk safely to both ends of the scaffold?

Correct

Part B

How close to the right end can he approach safely?

Express your answer using two significant figures.

Part C

How close to the left end can he approach safely?

Express your answer using two significant figures.

Problem 12.71

A 70.0-kg painter is on a uniform 21-kg scaffold supported from above by ropes. There is a 3.3-kg pail of paint to one side, as shown (Figure 1) .

Part A

Can the painter walk safely to both ends of the scaffold?

Yes No

Correct

Part B

How close to the right end can he approach safely?

Express your answer using two significant figures.

dright =   cm  

Part C

How close to the left end can he approach safely?

Express your answer using two significant figures.

dleft =   cm   1.0 m 4.0 m 1.0 m 1.0 m

Explanation / Answer

Let us assume that the painter can go till X distance right from the right rope.

so the moment about right rope should be zero

so moment due to the painter = moment due to paint + moment due to weight of scaffolding

so, 70 x X = 3.3 x 3 + 21 x 2 ( g is not added as it will be eliminated)

so, X = 0.741 m

so the painter can approach 0.741m to the right of right rope safely.

Let us assume that the painter can go till Y distance left from the left rope.

so the moment about left rope should be zero

so moment due to the painter = moment due to paint + moment due to weight of scaffolding

so, 70 x Y = 3.3 x 1 + 21 x 2 ( g is not added as it will be eliminated)

so, X = 0.647 m

so the painter can approach 0.647m to the left of left rope safely.

so the answers are as below:

a. No

b. 1-0.741 =0.26 m or 26 cm

c. 1-0.647 = 0.353 or 35 cm

all the best in the course work

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