A 8 m bar is pivoted at 5 m from the left end. With a force of 15 N on the left end and 20 N on the right end, what moments occur and in which direction does the bar rotate?

To determine the correct answer regarding the moments and the direction of rotation of the bar, it's essential to calculate the moments created by the forces acting on it relative to the pivot point.

The pivot point is located 5 meters from the left end, meaning the distances to each end of the bar from this pivot are as follows:

• The left end (where the 15 N force is applied) is 5 m from the pivot.

• The right end (where the 20 N force is applied) is 3 m from the pivot.

The moment (or torque) is calculated by multiplying the force applied by the distance from the pivot.

For the force on the left end:

• Moment from the 15 N force = 15 N * 5 m = 75 Nm. This force creates a counter-clockwise moment since it tends to rotate the bar upwards on the left side.

For the force on the right end:

• Moment from the 20 N force = 20 N * 3 m = 60 Nm. This force creates a clockwise moment since it tends to rotate the bar downwards on the right side.

Next, we compare the magnitudes of these moments:

• The counter-clockwise moment is 75