2 inches 3 inches Pivot. If 60 lbs. of force must be applied to the valve for it to open, how much upward force must push rod X apply for the valve to open?

A 60 lbs

B. 40 lbs

C 30 lbs

D. 20 lbs

E 15 lbs

We can solve this problem by stating that the summation of momentums must be zero. That is, the momentum at one end of the pivot must be equal to the momentum at the other end.

Momentum 1 = Momentum 2

Since Momentum is the product of Force and Distance, and with this rule created, we can say that:

F1 * d1 = F2 * d2

Where,

F1 = 60 lbs

d1 = 2 inches from the pivot

F2 = unknown X

d2 = 3 inches from the pivot

Substituting to the equation to find for F2:

60 lbs * 2 inches = F2 * 3 inches

F2 = 40 lbs

Therefore 40 lbs of upward force must be pushed to open the valve.

Answer: B