Question

A diver of weight 450 N stands at the end of a diving board of length L = 4.1 m and negligible mass (the figure). The board is fixed to two pedestals separated by distance d = 1.8 m. Take the upward direction to be positive. Of the forces acting on the board, what are (a) the force from the left pedestal and (b) the force from the right pedestal?

Answer 1

Since Figure is not given, So I'm assuming that

F1 = Force on left pedestals at x = 0

F2 = Force on right pedestals at x = d

W = Weight of diver, located at x = L

Now Using force balance in vertical direction

Fnet = F1 + F2 - W = 0

F1 + F2 = W

Using torque balance about right pedestals

Net torque = F1*d + W*(L - d) = 0

from above equation

F1 = -W*(L - d)/d

Using given values:

W = 450 N

L = 4.1 m & d = 1.8 m

So,

F1 = -450*(4.1 - 1.8)/1.8 = -575 N

Magnitude of F1 = 575 and negative sign means force F1 is downward

Part B.

F1 + F2 = W

F2 = W - F1

F2 = 450 - (-575) = +1025 N

Positive sign means force is upward.

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