To find the effort force when given the resistance force and the actual mechanical advantage (AMA), you can use the formula:
\[ \text{AMA} = \frac{\text{Resistance Force}}{\text{Effort Force}} \]
Rearranging the formula to solve for the effort force gives:
\[ \text{Effort Force} = \frac{\text{Resistance Force}}{\text{AMA}} \]
Now, substituting the given values:
- Resistance Force = 158 N
- AMA = 4
Let's calculate the effort force:
\[ \text{Effort Force} = \frac{158 , \text{N}}{4} = 39.5 , \text{N} \]
Therefore, the effort force is 39.5 N.