Question

why does the turning effect of force increase when force is applied from larger perpendicular distance of point at which force is applied?

Please tell me the reason. Please ​

Answer 1

Answer:

Chapter 1.1 - Turning Effect of Force and Equilibrium Exercise 13

Question 1

Define moment of force and state its SI unit.

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).

Question 2

Its moment of a force scalar or a vector quantity?

Solution 2

The moment of force is a vector quantity.

Question 3

Name the physical quantity whose SI unit is Nm.

Solution 3

Torque

Question 4

What is meant by a translational motion? Give one example.

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.

Question 5

What is meant by a rotatory motion? Give one example.

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.

Question 6

What is the relationship between Nm and dyne cm?

Solution 6

1 Nm = 107 dyne cm

Question 7

State the factors on which moment of force about a point depends.

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.

Question 8

What do you understand by the clockwise and anti clockwise moment of force?

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.

Question 9

State the condition when a force produces 

           (i) linear motion. 

           (ii) rotational motion, in a body.

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.

Question 10

Why is easier to open a door by applying the force at its free end?

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.

Question 11

Why does a spanner have a long handle?

Solution 11

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

Question 12

What do you mean by equilibrium of a body?

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.

Question 13

State the condition when a body is in (i) static, (ii) dynamic, equilibrium. Give one example each of static and dynamic equilibrium.

(b) Algebraic sum of moments acting on the body should be zero.

Question 15

State the principle of moments.

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.

Question 16

Draw a neat labeled diagram to show the direction of two forces acting on a body to produce rotation in it. Also mark the point about which rotation takes place.

Solution 16

Question 17

Give two examples of couple action in our daily life.

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

Question 18

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'.