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# Class 10 FRANK Solutions Physics Chapter 1.1 - Turning Effect of Force and Equilibrium

Use Frank Solutions for ICSE Class 10 Physics Chapter 1.1 Turning Effect of Force and Equilibrium to revise key chapter concepts. Learn to define moment of force or explain what’s meant by equilibrium of a body. Refer to our textbook solutions to revise Physics concepts such as couple, moment of couple, rotatory motion, translational motion etc.

Practise TopperLearning’s Frank Solutions for ICSE Class 10 Physics to grasp the turning effect of force and equilibrium. Score better in your Physics exam by benefitting from our chapter resources such as concept videos, question papers, online tests and more.

## Turning Effect of Force and Equilibrium Exercise 13

### Solution 1

The turning effect produced by a force on a rigid body about a point, pivot or fulcrum is called the moment of force or torque. It is measured by the product of force and the perpendicular distance of the pivot from the line of action of force.
Moment of a force = Force x perpendicular distance of the pivot from the force.
Its SI unit is newton-metre (Nm).

### Solution 2

The moment of force is a vector quantity.

Torque

### Solution 4

When some force is applied on a rigid body free to move and the body starts moving along a straight path in the direction of force. This is known as linear or translational motion. Points on the rigid body, undergo displacements forming parallel lines and magnitude of displacement is the same for individual point.
e.g. the motion of a bullet fired from a gun, a ball thrown straight up and falling back straight down.

### Solution 5

If a rigid body is pivoted at a point, then the applied force will rotate the body about the fixed point or about the axis passing through the fixed point. This motion is called rotational motion.
e.g. Earth's rotation about its axis, wheels of car in motion.

### Solution 6

1 Nm = 107 dyne cm

### Solution 7

The factors on which the moment of force about a point depends are:
1. The magnitude of force applied.
2. The distance of the line of action of the force from the axis of rotation.

### Solution 8

If the turning effect on the body is clockwise, moment of force is called the clockwise moment and is taken as negative.
If the turning effect on the body is anticlockwise, moment of force is called the anticlockwise moment and is taken as positive.

### Solution 9

(i) If a rigid body is free to move, the applied force will cause translational motion.
(ii) If a rigid body moves around a center or is pivoted at a point, the applied force will cause rotational motion.

### Solution 10

This is so because near the free end, the distance of the point of application of force from the axis of rotation becomes maximum, so the torque (= Force x perpendicular distance of the pivot from the force) is very large and hence it is easier to open the door.

### Solution 11

A long handle facilitates increased torque with small application of force; hence a spanner has a long handle.

### Solution 12

A body is said to be in equilibrium under the action of a number of forces, if the forces are not able to produce any change in the state of rest or of uniform motion or uniform rotation.
Equilibrium is a state of zero acceleration.

### Solution 13

(i) The conditions for static equilibrium are:
(a) The sum of the (vector) forces must equal zero, i.e. ? F = 0
(b) The sum of the torques must equal zero; i.e. ? ? = 0.
(ii) The conditions for dynamic equilibrium are:
(a) The body should have a broad base.
(b) Centre of gravity of the body should be as low as possible.
(c) Vertical line drawn from the centre of gravity should fall within the base of the support.
Examples:
Static equilibrium: a box at rest on a floor; there is a gravitational force pulling the object to the earth, but there is also an equal and opposite force applied by the floor to the box (pushing up).
Dynamic equilibrium: A rock travelling across the cosmos, far enough away from any other object (so as not to be affected by gravity - in other words, in zero gravity conditions); the rock continues to travel in a straight line at uniform velocity either for eternity, or until acted upon by an external unbalanced force.

### Solution 14

Conditions for equilibrium:
(a) Vector sum of forces acting on the body should be zero.
(b) Algebraic sum of moments acting on the body should be zero.

### Solution 15

Principle of moments: If a body is in equilibrium under the action of number of force, then the sum of clockwise moments is equal to the sum of anticlockwise moments.

### Solution 16 ### Solution 17

Examples of couple action in daily life:
(i) Opening and closing the cap of a bottle
(ii) Turning a key in a lock

### Solution 18

(i) Force 'R' has the least moment about 'O' because its perpendicular distance is least from 'O'.
(ii) Force 'P' has the maximum moment about 'O' because its perpendicular distance is maximum from 'O'.

## Turning Effect of Force and Equilibrium Exercise 14

### Solution 19

Two equal and opposite parallel forces acting along different lines on a body constitute a couple.
Effect of couple: It produces angular acceleration.

### Solution 20

The turning effect of a couple is called the moment of couple and is calculated by the product of either of the forces and the perpendicular distance between them.
Its SI unit is Nm.

### Solution 21 ### Solution 22 ### Solution 23 ### Solution 24

Conditions of equilibrium for a rigid body:
1. The body should have a broad base.
2. Center of gravity of the body should be as low as possible.
3. Vertical line drawn from the center of gravity should fall within the base of
support.
4. Vector sum of forces acting on the body should be zero.
5.  Algebraic sum of moments acting on the body should be zero.