Chapter 5: Turning Effect of Forces

Question 1

What is the moment of a force?

Answer 1

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

Question 2

What is moment affected by?

Answer 2

1. Perpendicular distance of the force from the pivot

2. Magnitude of the force

Question 3

What is the formula of a moment of a force?

Answer 3

Moment of a force (Nm)
= F x D
where,
F = Force(N)
D = Perpendicular distance from the pivot(m)

Question 4

What is the SI Unit and physical quantity of a moment?

Answer 4

SI Unit: Newton metre (Nm)

Phy Quantity: Vector

Question 5

What is clockwise moment?

Answer 5

The direction of rotation caused by the force follows the direction of a clock’s hand

Question 6

What is anti clockwise moment?

Answer 6

The direction of rotation caused by the force is in the opposite direction to the movement of a clock’s hand

Question 7

What does the Principle of Moments state?

Answer 7

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

CW = ACW
f1 x d1 = f2 x d2

Question 8

What is the two conditions that an object must satisfy in equilibrium?

Answer 8

1. The resultant force on the object is zero

2. The resultant moment on the object is zero

Question 9

What is the centre of gravity?

Answer 9

The point through which its whole weight appears to act for any orientation of the object

Question 10

What is stability?

Answer 10

The ability of an object to return to its original position after it has been tilted slightly

Question 11

What are the types of equilibriums?

Answer 11

1. Stable
2. Unstable
3. Neutral

Question 12

How to increase stability?

Answer 12

1. Lower its centre of gravity

2. Increase the area of its base

Question 13

What are the properties of stable equilibrium?

Answer 13

1. A tilted object will return to its original position
2. The line of action through its weight lies within its base
3. The centre of gravity is raised before falling back to its original height

Question 14

Why an object is stable?

Answer 14

The line of action of its weight below the centre of gravity falls within its base. An anticlockwise moment is produced by its weight above the edge to make it turn to the left and return to its original position

Question 15

What are the properties of a unstable equilibrium?

Answer 15

1. A tilted object will move away from its original position
2. The line of action through its whole weight lies outside its base
3. The centre of gravity is lowered and continue go lower

Question 16

Why is an object unstable?

Answer 16

The line of action of its weight below the centre of gravity lies out of its base. A clockwise moment about the edge is produced by its weight causing it to tapple to the right

Question 17

What are the properties of neutral equilibrium?

Answer 17

1. The object stays in position which it is displaced
2. The line of action through its base and point of contact coincide
3. The centre of gravity remains at the same height