A 20.0-m-long uniform beam weighing 630 N rests on walls A and B, as shown in th

Question

A 20.0-m-long uniform beam weighing 630 N rests on walls A and B, as shown in the figure (Figure 1).

Part A

Part complete

Find the maximum weight of a person who can walk to the extreme end D without tipping the beam.

Express your answer to two significant figures and include the appropriate units.

630 N

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Correct

Part B

Part complete

Find the forces that the walls A and B exert on the beam when the person is standing at D.

Express your answers using two significant figures separated by a comma.

0,1300

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Correct

Part C

Part complete

Find the forces that the walls A and B exert on the beam when the person is standing at a point 2.2 m to the right of B.

Express your answers using two significant figures separated by a comma.

150,1100

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Correct

Part D

Find the forces that the walls A and B exert on the beam when the person is standing 2.7 m to the right of A.

A 20.0-m-long uniform beam weighing 630 N rests on walls A and B, as shown in the figure (Figure 1).

Part A

Part complete

Find the maximum weight of a person who can walk to the extreme end D without tipping the beam.

Express your answer to two significant figures and include the appropriate units.

(mg)max =

630 N

SubmitPrevious Answers

Correct

Part B

Part complete

Find the forces that the walls A and B exert on the beam when the person is standing at D.

Express your answers using two significant figures separated by a comma.

FA, FB =

0,1300

  N  

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Correct

Part C

Part complete

Find the forces that the walls A and B exert on the beam when the person is standing at a point 2.2 m to the right of B.

Express your answers using two significant figures separated by a comma.

FA, FB =

150,1100

  N  

SubmitPrevious Answers

Correct

Part D

Find the forces that the walls A and B exert on the beam when the person is standing 2.7 m to the right of A.

Figure 1 of 1> 20.0 m 3.0 m 12.0 m

Explanation / Answer

(a)We have

?M = 0 = W * 5m - 630N * 5m
since the force on the left wall is zero at the tipping point,
Then max weight is simply the weight of unifrom beam i.e,

W = 630 N

(b) As told above,

Fa = 0 N.

Fb = 630N + 630N = 1240 N
(vertical forces must sum to zero)

(c) Let's sum the moments about A:
?M = 0 = Fb * 12m - 630N * (14.2)m - 630N * 7.1m

or Fb = 1118.25 N
Therefore

Fa = 630N + 630N - 1118.25 N = 141.75 N

(d) let's again sum the moments about A:
?M = 0 = Fb * 12m - 630N * 2.7m - 630N * 7.35m

therefore

Fb = 1041.86 N
and Fa = 630N + 630N - 1041.86 N = 218.14 N

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