A 20.0 m long uniform beam weighing 790 N rests on walls A and B, as shown In th

Question

A 20.0 m long uniform beam weighing 790 N rests on walls A and B, as shown In the figure below. (a) Find the maximum weight of a person who can walk to the extreme end D without tipping the beam. 790 N (b) Find the forces that the walls A and B exert on the beam when the same person is standing at point D. 0 N (wall A) 1570 N (wall B) (c) Find the forces that the walls A and B exert on the beam when the same person is standing at a point 2.0 m to the right of B. 193 N(wall A) 1377 N(wall B) (d) Find the forces that the walls A and B exert on the beam when the same person is standing 2.0 m to the right of A. N (wall A) N(wall B)

Explanation / Answer

part d:

the person is standing 2 m to the right of A.

let reaction force at A be Fa and reaction force at B be Fb.

both the reaction forces in vertically upward direction.

balancing total forces in vertical direction:

Fa+Fb=weight of the person + weight of the beam

==>Fa+Fb=790+790=1580 N...(1)

balancing torque about point B:

Fa*12=weight of the beam*5+weight of the person *(12-2)

==>Fa*12=790*5+790*10

==>Fa=(790*5+790*10)/12=987.5 N

then Fb=1580-Fa=592.5 N

so reaction force by wall A is 987.5 N

reaction force by wall B is 592.5 N

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