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
