# Physics

posted by .

A construction supervisor of mass M = 83.7 kg is standing on a board of mass m = 30.5 kg. The board is supported by two saw horses that are a distance of 4.50 m apart. If the man stands a distance x1 = 1.30 m away from saw horse 1 as shown, what is the force that the board exerts on that saw horse?

• Physics -

Set the total moment about saw horse 2 equal to zero. Call the upward force at saw horse 1 "F1".

F1*4.50 = Mg(4.50 - 1.30) + mg(2.25)
Solve for F1. The number 2.25 meters appears because the weight of the board acts through the center of gravity.

• Physics -

I still don't quite understand how you got 2.25 meters...

• Physics -

2.25 m is the location of midpoint of the board, where the board's weight acts. That is measured from saw horse 2. I am assuming that the saw horses are at the ends. If a figure (which you did not provide) says otherwise, use the appropriate distance.

• Physics -

ok so i solved all that out and it said i was wrong and told me this

There are two forces acting on the saw horses. One is due the weight of the board. This is evenly distributed between the two saw horses, because the board is placed symmetrically on them.

The other force acting on the saw horse is due to the weight of the man. If the man was standing exactly in the middle, his weight would also be distributed evenly over both saw horses. However, he is standing off to one side, and so his weight gets distributed proportionally to the distances of the man to the saw horses.

To do the math, it is perhaps easiest to use the top of saw horse 2 as the pivot points for calculating the torques on the board. (They have to add up to zero!).

## Similar Questions

1. ### physics

A construction supervisor of mass M = 83.7 kg is standing on a board of mass m = 30.5 kg. The board is supported by two saw horses that are a distance of 4.50 m apart. If the man stands a distance x1 = 1.30 m away from saw horse 1 …
2. ### Physics

A sturdy wooden board, 4.0 meters long and with a mass of 32 kg, rests on two supports (labeled L and R) placed 1.2 m from each end as shown in the figure below. (a) Suppose that a man with a mass of 60 kg stands at the center of the …
3. ### physics

A diver of mass 68.9 kg stands at the end of a diving board of mass 24.5 kg and length L = 3.29 m. The diving board is supported at two locations, labeled A and B on the diagram. A and B are separated by a distance d = 0.74 m. Observe …
4. ### physics

Persons A and B are standing on a board of uniform linear density that is balanced on two supports, as shown in the figure. What is the maximum distance x from the right end of the board at which person A can stand without tipping …
5. ### Physics

Two identical rollers are mounted with their axes parallel, in a horizontal plane, a distance 2d = 40.4 cm apart. The two rollers are rotating inwardly at the top with the same angular speed. A long uniform board is laid across them …
6. ### Physics

Two identical rollers are mounted with their axes parallel, in a horizontal plane, a distance 2d = 40.4 cm apart. The two rollers are rotating inwardly at the top with the same angular speed. A long uniform board is laid across them …
7. ### Physics

Two identical rollers are mounted with their axes parallel, in a horizontal plane, a distance 2d = 40.4 cm apart. The two rollers are rotating inwardly at the top with the same angular speed. A long uniform board is laid across them …
8. ### Physics

Two identical rollers are mounted with their axes parallel, in a horizontal plane, a distance 2d = 40.4 cm apart. The two rollers are rotating inwardly at the top with the same angular speed. A long uniform board is laid across them …
9. ### Physics

A diver stands on the end of a diving board as shown in the figure on the right. The mass of the diver is 58 kg and the mass of the uniform diving board is 35 kg. Calculate the magnitudes and directions of the forces exerted on the …