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So with the above example it is to be understood that the terms ‘moving’ and ‘not moving’ are relative terms, dependent on the surroundings. Whether we look at an apple falling from a tree, or the chemical and nuclear reactions, or the case of heart pumping blood, everything is moving and this change in position is termed as ‘Motion’.

Motion is the change in an object’s position with respect to its surroundings. Motion is also defined as the ‘process of any movement’ or the ‘action of being moved’.

The study of motion plays a huge and a very important role in Physics. The concepts of Physics always revolve around the aspect of ‘motion’. In Physics, the study of the motion of objects is termed as ‘Mechanics’. The branch of Mechanics which involves describing the motion of objects using various tools such as equations, diagrams and graphs is known as ‘Kinematics’. This motion is usually described in terms of distance, time, displacement, velocity and acceleration.

Let us look at an example below which tells us the difference between distance and displacement.

Let a car starting at point P travel 3m down South and then 4m in the East direction as shown in the figure on the right.

The car’s initial position is at point P and its final position is at point B.

The total distance travelled by the car = PA + PB = 3m + 4m = 5m

However, the displacement of the car must be the shortest distance from the initial point to the final point, and this implies displacement = PB

We can calculate PB by using Pythagorean Theorem ==> PB = √(3

Hence the displacement of the same car is 5m.

Velocity is a physical quantity which describes the rate at which an object changes its position from one point to another. Velocity is a vector quantity as magnitude and direction both apply to it.

If an object has an initial velocity of ‘u’ and final velocity of ‘v’, then the average acceleration of that object in a certain time interval of ‘t’ can be calculated using the formula shown below:

a)

b)

Motion is primarily classified into 3 types based on the path taken by the object in motion:

1)

Examples: A bus moving on the road, path of a moving vehicle on a straight road.

2)

Examples: The wheel of any moving vehicle, hands of a clock, spinning top etc.

3)

Examples: Swinging pendulum, swings in a playground, swinging cradle etc.

There are other types of motion such as vibrational motion, periodic motion, random motion which can also be observed in our daily life.

Isaac Newton, a scientist in the 17

The first law states that ‘’an object at rest stays in rest and an object in motion continues to stay in motion (with the same speed in the same direction), unless acted upon by an unbalanced force”.

This law brings out an underlying concept known as the ‘Inertia’. Inertia can be defined as the tendency of an object to resist a change in its motion.

The second law states that ‘’the acceleration of an object as produced by a net force is inversely proportional to the mass of the object, and is directly proportional to the magnitude of the net force (direction being the same as the net force)”.

This law when translated to a mathematical statement can be written as shown below:

The above equation when rearranged gives us:

When objects come in contact with each other, as a result of those interactions the push or pull that acts upon the objects is termed as ‘Force’. There are forces which are termed as ‘Contact Forces’ as they result from interactions that come through contact. Examples of contact forces are normal force, tension force, frictional force, and any applied forces. There are other types of forces that show effect even from a distance. Examples of such forces are gravitational force, magnetic force, electrical force etc. According to Newton, whenever objects interact with each other they apply force on each other. And in this interaction the 2 forces that act upon the objects in contact, are the ‘action-reaction forces’.

So Newton’s third law states that, ‘every action has an equal and opposite reaction’.

So this law clearly explains that forces always come in pairs, and when the objects are in contact with each other the size of forces (magnitude) on the first object by the second, and on the second object by the first are the same. The direction of force exerted on the first object is opposite to the direction of force exerted on the second object.

When a person sits on the chair, the person exerts downward force on the chair and the chair exerts upward force on the person. This is an action-reaction pair resulting from the contact between the person and the chair.

Consider an object travelling on a straight line with an initial velocity of ‘u’ at t = 0, and reaches final velocity in a certain time interval of ‘t’. If the acceleration during this time interval is ‘a’, then the first equation of motion is given as:

Acceleration, a = Change in velocity/ Time

a = (v – u) / t

This can also be written as ==> a * t = (v – u)

The above when rearranged gives us:

Given: Car starts at rest ==> at t = 0, initial velocity, u = 0m/s

After t = 6 seconds, final velocity, v = 30m/s

Acceleration, a = ?

From the first equation of motion we have: v = u + at

This implies: 30 = 0 + a*6 ==> 30 = 6a ==> a = 30/6 = 5m/s

Therefore, the acceleration of the car is 5m/s

Let u = initial velocity of an object

v = final velocity of an object

t = total time taken for the object to travel a displacement = ‘d’

a = acceleration of the object

We know that: Average Velocity = Total displacement covered / Total time taken

Now, Average Velocity can be written as the average of the initial velocity and the final velocity of an object.

Therefore, average velocity = (u + v)/2. Substituting this average velocity in the above equation we get:

(u + v)/2 = Total displacement covered / Total time taken

==>(u + v)/2 = d/t. This gives: (u + v) = 2d/t

Now from the First Equation of Motion we have: v = u + at. Substituting this into the above equation we get:

(u + u + at) = 2d/t ==> 2u + at = 2d/t ==> t * (2u + at) = 2d ==> 2ut + at

Now solving for ‘d’, we get: d = 1/2 * (2ut + at

Given: Initial velocity of the car, u = 0m/s

Acceleration, a = 8m/s

Time taken, t = 4seconds

Displacement, d = ?

From the given information, here we can use the Second Equation of Motion.

Therefore, d = ut + ½* at

Hence the displacement of Andrew’s car during the given time period is 64m

Let u = initial velocity of an object

v = final velocity of an object

t = total time taken for the object to travel a displacement = ‘d’

a = acceleration of the object

From the First Equation of Motion we have: v = u + at.

This equation when rearranged gives us (v- u) = at Equation 1

Now, we know that: Average Velocity = Total displacement covered / Total time taken

(u + v)/2 = d/t. Hence (v + u) = 2d/ t Equation 2

Now multiplying both Equation 1 and Equation 2 we get: (v – u) (v + u) = at * 2d/t

Therefore we get:

Given: Initial velocity, u = 4m/s

Final velocity, v = 10m/s

Distance covered, d = 20m

Acceleration, a = ?

From the given information, here we can use the Third Equation of Motion.

Therefore, v

Now solving for ‘a’ we get: a = 84/40 ==> a = 2.1m/s