Moments, levers and gears | Exit Quiz | Oak National Academy

Match the following key terms to their definition.

• gear

• a lever that increases the size of an applied force

• force multiplier

• a toothed wheel that rotates and is used to transfer a moment

• equilibrium

• a lever that increases the distance an applied force moves through

• moment

• the turning effect of a force, measured in newton metres (Nm)

• distance multiplier

• the state of an object if there is no resultant force or moment on it

Answer explanation

Levers and gears produce moments in useful ways. Force and distance multipliers are levers that are used in different ways. A moment is the turning effect of a force. An object is in equilibrium if no resultant force or resultant moment acts on it.

In how many of the following situations is the box in equilibrium?

• 0

• 1

• 2

• 3

Answer explanation

First box: no resultant force but a resultant clockwise moment. Second box: no resultant moment (forces act in line with centre of box and each other) but a resultant force of 6 N. Third box: no resultant moment but a resultant force of 8 N.

A lever can be a force multiplier or a distance multiplier. Which of the following levers is a distance multiplier?

• 
• 
• 

Answer explanation

When a lever is used as a distance multiplier, the applied force is greater than it would be without the lever. However, although more force is required, the load can be moved over a greater distance for the same amount of effort.

What is the moment about the pivot caused by the force in the following diagram?

• 40 Nm clockwise

• 40 Nm anticlockwise

• 1.6 Nm clockwise

• 1.6 Nm anticlockwise

Answer explanation

Moment = force × distance (normal to direction of force) = 8.0 × 0.20 = 1.6 Nm. The moment is anticlockwise because it will make the object rotate in the opposite direction to the hands of a clock.

What is the moment caused by the force about the pivot in the following diagram? You need to choose the correct distance for your calculation.

• 33 Nm

• 39 Nm

• 54 Nm

• 58 Nm

Answer explanation

The perpendicular distance between the direction of the 30 N force and the pivot is 1.3 m. Moment = force × distance normal to direction of force = 30 N × 1.3 m = 39 Nm.

The diagram shows a set of gears, X and Y, in a machine. Using an attached handle, a person produces a moment of 18 Nm about gear X, which rotates once. Which of the following statements are correct?

• Gear Y makes 3 rotations.

• The moment of gear Y is Nm.

• The moment of gear Y is 18 Nm.

• The moment of gear Y is 36 Nm.