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

Match the following key terms to their definition.

• moment

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

• distance multiplier

• a lever that increases the size of an applied force

• equilibrium

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

• gear

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

• force multiplier

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

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.