12.1 Conditions for Static Equilibrium

Solve the example by choosing the pivot at the location of the rear axle.

Explain which one of the following situations satisfies both equilibrium conditions: (a) a tennis ball that does not spin as it travels in the air; (b) a pelican that is gliding in the air at a constant velocity at one altitude; or (c) a crankshaft in the engine of a parked car.

What can you say about the velocity of a moving body that is in dynamic equilibrium?

What three factors affect the torque created by a force relative to a specific pivot point?

For the next four problems, evaluate the statement as either true or false and explain your answer.

If there is only one external force (or torque) acting on an object, it cannot be in equilibrium.

For the next four problems, evaluate the statement as either true or false and explain your answer.

If an odd number of forces act on an object, the object cannot be in equilibrium.

For the next four problems, evaluate the statement as either true or false and explain your answer.

What purpose is served by a long and flexible pole carried by wire-walkers?

When opening a door, you push on it perpendicularly with a force of 55.0 N at a distance of 0.850 m from the hinges. What torque are you exerting relative to the hinges?

Two children push on opposite sides of a door during play. Both push horizontally and perpendicular to the door. One child pushes with a force of 17.5 N at a distance of 0.600 m from the hinges, and the second child pushes at a distance of 0.450 m. What force must the second child exert to keep the door from moving? Assume friction is negligible.