[Physics Class Notes] on Speed of Moving Objects Pdf for Exam

An object is said to be moving only when it changes its position. Therefore, a moving object is characterized by its position, its direction of motion, and its direction of movement.

Let’s consider a block of mass, ‘m’ kept on the table.

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Now, if we give it a push, it starts moving in the direction of force.

Newton’s first law states that if an external force is applied to this block, it changes its position or sets into motion.

Before learning about the Speed of moving projects, let us discuss moving objects.

Moving Objects

When an object changes its position, we can say it is moving.

We can characterize a moving object based on its direction of motion, movement, and position.

If we give this object a push, it starts to move in the force we push it.

Newton’s First Law is applied here. It states that if an external force is applied to this block, it will change its position or set into particular Motion.

Motion Can Be Found In Many Real-life Objects

We can find it in objects like:

Types of Motion

There are several types of Motion. Let us look at these different types in detail.

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One example is, Planets revolving around the sun in a fixed interval of time.

This Motion can also be referred to as simple harmonic motion.

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One example is when we tie a stone to a string and apply even a little force to the string. The stone starts rotating at a fixed point.

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Examples Of Moving Objects

Motion can be of various types, some of them are discussed with examples below:

1. Rectilinear Motion: Motion of a body along the straight line.

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2. Periodic Motion: The motion repeated after a fixed interval of time.

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The revolution of planets around the sun in a fixed interval of time. 

Such a motion is also called the simple harmonic motion.

3. Circular Motion: A body follows a circular locus such that the force required to move a body uniformly in a circle acts along the radius and towards the center of the circle. With continuous change in the direction of motion of the body, there is a change in velocity of the body and hence, it undergoes an apparent acceleration called the centripetal acceleration. For example,  when a stone is tied to a string and on applying the force, the stone starts rotating about a fixed point.

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What Is The Speed of Moving Objects?

The rate at which an object changes its position is called its Speed. 

We can define the a body’s Speed as:

s  = Distance travelled/ time taken

Speed is a scalar quantity because it has a magnitude, but the direction of a body is unknown.

If we take a body with the mass of ‘m’ and push it with force ‘F,’ it changes its position because of Speed.

In terms of the SI system, we measure it in meters per second, while in the cgs system, we measure it in cm/s.

We can understand this with an example,

If we take a vehicle and its Speed is constant, we can calculate its constant Speed.

This will mean that if it is in a uniform motion, we will cover equal distances in equal interviews of time. 

But suppose that the same body covers an equal distance in equal intervals of time and vice versa, no matter how small the intervals are. In that case, we can calculate such variations in Speed by calculating an average speed.

The Average Speed = Vₐᵥ = Total distance travelled/Total time taken = 2 v₁v₂/(v₁+v₂) m/s

Take an example of a path in which a body starts moving from a point to reach another point.

Here we can observe the distance between two points during the time t represented by a vector drawn from the initial to the final position.

What Is The Velocity of a Moving Object?

Taking displacement into consideration, the shortest distance to reach this destination would be:

A body will move from A to reach B in time, ‘t.’

Here, we observe the distance between these two points in time t and we can represent this by a vector drawn from the starting to the ending position.

If we take displacement into consideration, it will be the shortest distance to reach that certain destination.

So, we will calculate velocity by,

V =  Displacement/ time taken (in m/s) = ΔX/Δ t = (X₂ – X₁)/(t₂ – t₁) m/s

A body in a circular motion will move with a constant velocity. The velocity vector will keep on changing this time.

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A body moving 5 m/s north is a vector.

Then it moves 5 m/s west , with the same speed moves to the south and then to the west.

Here, the magnitude (speed) is the same while the direction is changing.

So, that’s why velocity is a vector quantity.

Slow and Fast Motion

Whether the body is moving slow or fast can be determined by measuring the relative velocity of both objects and comparing them to each other. We can define it as the rate at which the relative position of an object changes concerning each other.

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If we take the example of a train and a car, both moving in the same direction. We can imagine that the car driver would be able to see the train passing it. This tells us that the train is in a fast motion.

But at the same time, the passenger in that train would observe the car and see that it was slow, which would tell us that the car is in slow motion.

Both the car and the train are moving here, but they have different velocities. By this, we understand that:

Here, these two vehicles (the train and the car) are moving with separate velocities.

Let us take the velocity of the train as v₁ and the car’s as v₂.

The relative velocity of train in comparison to the car’s velocity, even when they are moving in the same direction, will be represented by:

v  =   (v₁ – v₂)

Hence, v₁ is greater than v₂ and v’s value is positive.

By this we conclude that:

• We can observe Slow Motion in the car’s movement with respect to the train as it is moving at a slower speed.

• Fast Motion can be observed in the train’s movement concerning the car as it moves faster.