Chap 5 Turning Effect of Forces

Question 1

Define the moment of a force

Answer 1

The moment of a force is the product of the force and the perpendicular distance from the pivot to the line of action of the force.

Question 2

What is the formula of the moment of a force?

Answer 2

Moment of a force = F (Force in N) x d (perpendicular distance from pivot in m)

Question 3

What is the Principle of Moments?

Answer 3

The Principle of Moments states that when a body is in equilibrium, the sum of clockwise moments about any pivot is equal to the sum of anti-clockwise moments about the same pivot.

Question 4

What are the 2 conditions for equilibrium?

Answer 4

For an object to be in equilibrium, all forces acting on it are balanced. (resultant force is zero) and the resultant moment about the pivot is zero. (Principle of Moment must apply)

Question 5

What are levers?

Answer 5

Levers are simple machines that make use of the Principle of Moments. When a force is applied at one end of the lever, a load may be lifted at the other end.

Question 6

What is the centre of gravity?

Answer 6

The centre of gravity of an object is defined as the point through which its whole weight appears to act for any orientation of the object.

Question 7

Define stability

Answer 7

Stability refers to the ability of an object to return to its original position after it has been tilted slightly.

Question 8

Describe the characteristics of a cone in Stable Equilibrium when a resultant force to the right direction is applied.

Answer 8

When a force is applied, the centre of gravity rises and then falls back again. The line of action of its weight lies inside the base area of the cone. The anticlockwise moment of its weight about the point of contact causes the cone to return to its original position.

Question 9

Describe the characteristics of a cone in Unstable Equilibrium when a resultant force to the right direction is applied.

Answer 9

When a force is applied, the centre of gravity falls and continues to fall further. The line of action of its weight lies outside the base area of the cone. The clockwise moment of its weight about the point of contact causes the toppling.

Question 10

Describe the characteristics of a cone in Neutral Equilibrium.

Answer 10

When a force is applied, the centre of gravity neither rises nor falls; it remains at the same level above the surface supporting it. The line of action of the two forces always coincides. There is no moment provided but its weight about the point of contact to turn the paper cone.

Question 11

What are 2 ways to increase the stability of an object?

Answer 11

Lowering the centre of gravity and increasing the width of its base.