3.4 Turning Forces

What is the turning moment of a force?

• The force applied to an object

• The distance from the pivot to the point of force application

• The product of the force and the perpendicular distance from the pivot to the line of action of the force

• The angle between the force and the lever arm

Which of the following factors affect the turning moment of a force?

• Magnitude of the force only

• Distance from the pivot only

• Both magnitude of the force and distance from the pivot

• None of the above

In the equation m = force x distance, what does 'm' represent?

• Mass

• Moment of force

• Magnitude of force

• Distance from the pivot

A force of 20N is applied to a lever arm 0.5m from the pivot. What is the turning moment?

• 10Nm

• 40Nm

• 25Nm

• 5Nm

A force of 50N is applied to a lever arm 1.2m from the pivot. What is the turning moment?

• 60Nm

• 41.67Nm

• 50Nm

• 1.2Nm

A force of 15N is applied to a lever arm to produce a turning moment of 45Nm. What is the distance from the pivot?

• 3m

• 15m

• 45m

• 0.33m

A force of 40N produces a turning moment of 120Nm. What is the distance from the pivot?

• 3m

• 480m

• 40m

• 0.33m

A seesaw is balanced with a child weighing 25kg sitting 2m from the pivot. Another child weighing 30kg sits on the other side. How far from the pivot should the second child sit to balance the seesaw?

• 1.67m

• 2m

• 2.4m

• 3m

A seesaw is balanced with a person weighing 70kg sitting 1.5m from the pivot. Another person weighing 50kg sits on the other side. How far from the pivot should the second person sit to balance the seesaw?

• 1.05m

• 1.5m

• 2.1m

• 3m

Seesaw Balance: A 40kg child sits 2 meters from the pivot point of a seesaw. How far from the pivot must a 30kg child sit to balance the seesaw?

Answer explanation

1. Seesaw Balance:

• - Let x be the distance the 30 kg child sits from the pivot.

• - 40 kg 2 m = 30 kg x

• - x = (40 * 2) / 30 = 8/3 meters ≈ 2.67 meters