Question

A weight of 720 N rests on a lever at a point 0.50 m from a support. On the same side of the support, at a distance of 3.0 m from it, an upward force with magnitude F is applied. Neglect the weight of the board itself. If the system is in equilibrium, what is F?

Answer 1

Answer:

120 N

Explanation:

weight (w) = 720 N

distance of weight from the support (s) = 0.5 m

upward acting force (F) = ?

distance of upward force from the support (L) = 3 m

If the system is in equilibrium, what is F?

since the system is in equilibrium Σ Torque = 0

where

• Σ Torque will be taken about the support which is the fulcrum of the lever.
• taking upward forces as negative and downward forces as positive

• neglecting the weight of the board
• Σ Torque = -FL + ws = 0

        -FL + ws = 0

        - (F x 3) + (720 x 0.5) = 0

          -3F + 360 = 0

           F = 360/3 = 120 N