Impulse and Impulsive Force: Definition, Formula, and Examples | 10th Science

Impulse - Definition, Formula, Examples

Impulse

A large force acting for a very short interval of time is called as ‘Impulsive force’. When a force F acts on a body for a period of time t, then the product of force and time is known as ‘impulse’ represented by ‘J’

Impulse, J = F × t (1.7)

By Newton’s second law

F = Δp / t (Δ refers to change)

Δp = F × t (1.8)

From 1.7 and 1.8

J = Δp

Impulse is also equal to the magnitude of change in momentum. Its unit is kg m s^–1 or N s. Change in momentum can be achieved in two ways. They are:

i. a large force acting for a short period of time and

ii. a smaller force acting for a longer period of time.

Examples:

• Automobiles are fitted with springs and shock absorbers to reduce jerks while moving on uneven roads.
• In cricket, a fielder pulls back his hands while catching the ball. He experiences a smaller force for a longer interval of time to catch the ball, resulting in a lesser impulse on his hands.

Inertia: Understanding Types and Examples | 10th Science, Chapter 1: Laws of Motion

Introduction 10th Science Chapter 1: Laws of Motion

Inertia - Types and Examples of Inertia

INERTIA

While you are travelling in a bus or in a car, when a sudden brake is applied, the upper part of your body leans in the forward direction. Similarly, when the vehicle suddenly is move forward from rest, you lean backward. This is due to, any body would like to continue to be in its state of rest or the state of motion. This is known as ‘inertia’.

The inherent property of a body to resist any change in its state of rest or the state of uniform motion, unless it is influenced upon by an external unbalanced force, is known as ‘inertia’.

In activity described above, the inertia of the coin keeps it in the state of rest when the cardboard moves. Then, when the cardboard has moved, the coin falls into the tumbler due to gravity. This happen due to ‘inertia of rest’.

1. Types of Inertia

a) Inertia of rest: The resistance of a body to change its state of rest is called inertia of rest.

b) Inertia of motion: The resistance of a body to change its state of motion is called inertia of motion.

c) Inertia of direction: The resistance of a body to change its direction of motion is called inertia of direction.

2. Examples of Inertia

• An athlete runs some distance before jumping. Because, this will help him jump longer and higher. (Inertia of motion)
• When you make a sharp turn while driving a car, you tend to lean sideways, (Inertia of direction).
• When you vigorously shake the branches of a tree, some of the leaves and fruits are detached and they fall down, (Inertia of rest).

Introduction to Laws of Motion | Chapter 1 | 10th Science

10th Science : Chapter 1 : Laws of Motion | Introduction

LAWS OF MOTION

INTRODUCTION

Human beings are so curious about things around them. Things around us are related to one another. Some bodies are at rest and some are in motion. Rest and motion are interrelated terms.

In the previous classes you have learnt about various types of motion such as linear motion, circular motion, oscillatory motion, and so on. So far, you have discussed the motion of bodies in terms of their displacement, velocity, and acceleration. In this unit, let us investigate the cause of motion.

When a body is at rest, starts moving, a question that arises in our mind is ‘what causes the body to move?’ Similarly, when a moving object comes to rest, you would like to know what brings it to rest? If a moving object speeds up or slows down or changes its direction. what speeds up or slows down the body? What changes the direction of motion?

One answer for all the above questions is ‘Force’. In a common man’s understanding of motion, a body needs a ‘push’ or ‘pull’ to move, or bring to rest or change its velocity. Hence, this ‘push’ or ‘pull’ is called as ‘force’.

Let us define force in a more scientific manner using the three laws proposed by Sir Isaac Newton. These laws help you to understand the motion of a body and also to predict the future course of its motion, if you know the forces acting on it. Before Newton formulated his three laws of motion, a different perception about the force and motion of bodies prevailed. Let us first look at these ideas and then eventually learn about Newton’s laws in this unit.

Mechanics

Mechanics is the branch of physics that deals with the effect of force on bodies. It is divided into two branches, namely, statics and dynamics.

• Statics:

  It deals with the bodies, which are at rest under the action of forces.

• Dynamics:

  It is the study of moving bodies under the action of forces. Dynamics is further divided as follows.

  • Kinematics:

    It deals with the motion of bodies without considering the cause of motion.

  • Kinetics:

    It deals with the motion of bodies considering the cause of motion.