Can You Apply a Single Force Anywhere to Get a Pure Rotation

MEE 150: Static Equivalency

Static equivalency revolves around the interplay between forces and couples. Statically equivalent loads are different ways of maintaining equilibrium. Here we investigate concepts of couples and statically equivalent loads.

Start at the position shown. Keep the thumbs fixed in position. Can you apply a single force to the bar anywhere to get a pure rotation around the center point?

Can you create a couple by applying two oppositely directed forces on the bar on either side of the center?

What is the effect of increasing the spacing between the two forces?

Can you create a couple by applying two forces to the bolts perpendicular to the bar?

Apply a couple using the nut driver at the center bolt and each of the bolts at the ends of the bar, keeping the axis of rotation at the center each time. What conclusion do you draw?

With the bar resting on the table, push on a center bolt. What happens to the bar?

Push on the bar near the right end of the bar without touching the bar otherwise. What happens?

While pushing on the right end of the bar, using your fingers apply a clockwise couple as shown. What happens?

While pushing on the right end of the bar, using the nut driver apply a couple at the center bolt and. What happens? Repeat with a couple at the right end bolt.

Placing the bar against a wall, balance it by holding it as shown.

With the bar against the wall, hang it using an elastic band. Push the bar up until it is horizontal. Then, apply a couple with your fingers at the center bolts. Repeat using the nut driver at the left end, center and right end bolts. What do you conclude?