Final answer:
The question lacks essential details to calculate the effort force. Lever principles are used for such calculations, but without specifics on the lever arm lengths or crate weight, a numerical answer cannot be determined.
Step-by-step explanation:
To determine the unknown effort force, we first need to understand the lever principle. The equation given, F_a = L_effort / L_lifting, allows us to calculate the mechanical advantage, which then helps us to find the effort force using the second formula, F_effort = F_lifting / F_a. Unfortunately, the question does not provide numerical values for the length of the lever arms or the weight of the crate, which are essential to calculate the effort force. In practical applications, such as lifting construction materials with a crane, working with a wheelbarrow, or calculating the efficiency of a lever, understanding the principle of lever arms and calculating the correct effort force is vital.
Without the specific measurements from the picture of the crate and lever, we cannot compute a numerical answer. A complete example to understand this concept better would be if a lever had an effort arm of 2m and a resistance arm of 0.5m, lifting a weight of 40N. The mechanical advantage would be F_a = 2m / 0.5m = 4. Then the effort required would be F_effort = 40N / 4 = 10N.