Measuring Rate of Change Motion: Definition, Types

We use common moving items around us, such as whether we look around us, monitor air flowing around us, or have clocks with moving hands. We all know that day and night are caused by the Earth's motion around the Sun, but seasons are also caused by it. To understand more about motion or rest, we must first understand what a reference point or stationary object is. We must consider a reference point, a stationary object, or the surroundings while commenting on the state of anything. The stationary object does not change its position at this reference point. 

Key Terms: Rest, Motion, Scalar and Vector quantities, Distance, Displacement, Magnitude

Also check: Potential Energy

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Rest and Motion

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Consider the case of a car parked in front of the house. Let's say it spends most of its time in place A and then transfers to location B after a while. That is, it has shifted its location in relation to the home, which is a stationary object.

And if that car remains in position A, it hasn't changed its position in relation to the house, indicating that it is at rest; hence, we define the terms rest and motion.

Rest: A body is said to be at rest when it does not change its position in response to its surroundings or reference point.

Motion: The body is in motion when it changes its position in relation to its surroundings or a reference point.

As a result, we can say that when an object moves or is in motion, it exhibits the properties listed below.

A moving object's characteristics include

With the passage of time, the moving object shifts its position. Now that we've seen that the movement of a car can be easily seen, implying that we don't need to concentrate as much, we need to keep verifying the movement of a clock arm, say the hour hand. This is because some motion is so quick that we can see it happening, while other motion is so slow that it can't be seen unquestionably.

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Types of Motion

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Linear - Linear motion is defined as movement that occurs in a straight line. Driving on straight roads, for example.

Rotational - We all know that the world spins on its axis, causing day and night, and that progress is rotational motion because it rotates on its axis, therefore we can describe it as rotational motion when a body rotates around a fixed axis.

Circular - We all come across roundabouts on the road, and we can't drive straight through them; instead, we must take the arched path that is the round motion. The body is considered to be in a circular motion if it travels along a curved path.

Vibratory - Everyone has probably tried their hand at playing the guitar. So, when you strike it with your finger, the string begins to vibrate, and the sound is produced. That motion is vibratory because it is created by particle vibrations, and it is when the body moves to and fro.

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Scalar and Vector Physical Quantities

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We learn a variety of physical quantities such as distance, velocity, and others. All of these values are classed as either scalar or vector depending on whether they provide complete information about magnitude (value) and direction or incomplete information such as only direction or only value.

Scalar Quantities

Scalar quantities are those that are dependent on magnitude rather than direction. Their symbol is used to represent them.

For example, what would you say if you travelled to Delhi to visit a relative and were asked about the distance? We likened it to a 250-kilometer run from Chandigarh. You don't tell him that it's 25 kilometers east and then west. We simply state 250 kilometers, which implies we only explain it in terms of magnitude and do not give any directions. As a result, it's a scalar quantity.

Vector Quantities

The magnitude and direction of physical quantities are both important. An arrow is added to their symbol to indicate them.

For instance, if you walk a straight short journey in a given direction, we can claim that you travelled 25 kilometers east. Because the direction is stated in this example, it is classified as a vector quantity.

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Reference Point and Reference Frame

• A reference point or origin is required to explain the position of an object. To one observer, an object may appear to be moving while to another, it appears to be motionless.
• For example, a passenger onboard a bus sees the other passengers resting, yet a spectator outside the bus sees the occupants moving.
• To make observations easier, a convention or a standard reference point or frame is required. The reference frame for all substances must be the same.

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Distance and Displacement

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Distance is the magnitude of the length contained by a moving item. It has no sense of direction. The shortest distance between two points, or the distance between the starting and final positions in terms of time, is called displacement. It has both magnitude and direction. The distance cannot be 0, but displacement can.

Read about: Difference between Speed and Velocity

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Magnitude

The magnitude of a physical quantity refers to its size or scope. We have scalar and vector quantities in physics. Only magnitude is used to express scalar numbers. Time, distance, mass, temperature, area, and volume are examples of variables.

The magnitude, as well as the direction of the entity, are articulated in vector quantities. Velocity, displacement, weight, momentum, force, acceleration, and so on are examples.

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Time, Average Speed and Velocity

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Time and Speed

Time is the duration of an incident expressed in seconds. The majority of physical phenomena take place over time. It's a number with a scalar value. The pace at which a distance change is referred to as speed. The speed of a body is determined by how far it travels in a given length of time. 

Speed = \(\frac{Distance}{Time}\)

Average speed = Total distance travelled/Total time taken

Non-uniform motion vs. uniform motion

Uniform motion occurs when an object travels the same lengths in the same amount of time. When an entity moves in a non-uniform manner, it covers uneven distances in equal amounts of time.

Velocity

Velocity is the rate of change of displacement. It's a quantity with a vector. The motion's direction is specified here.

Velocity = \(\frac{Displacement}{Time}\)

Average velocity = (Initial Velocity + Final Velocity)/2 = \(\frac{u+v}{2}\)

Acceleration

The rate of change of velocity is referred to as acceleration. It's a quantity with a vector. In non-uniform motion, velocity changes with time, i.e., the change in velocity is not zero. The letter "a" stands for it.

Acceleration = Change in Velocity/Time

Where, 

• v(final velocity)
•  t(time taken)
•  u(initial velocity)

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Equations of Motion

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Three equations can be used to describe the motion of an entity travelling at uniform acceleration, namely:

(i) v = u + at

(ii) v² – u² = 2as

(iii) s = ut + \(\frac{1}{2}\)at²

Uniform Circular Motion

• When an object moves in a circular direction with a constant speed, it is referred to as uniform circular motion.
• As the direction changes, the velocity changes as well.
• The rate of acceleration is constant.

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Things to Remember

• The overall distance travelled by an object per unit time is known as speed. The metric unit of speed is the metre per second (m/s).
• Velocity is a vector quantity defined as the rate at which an object's position changes in relation to a frame of reference over time.
• The rate of change of displacement is the same as the velocity of an item.
• The magnitude of a displacement equals the actual distance travelled by a body in a given time when it travels in a uniform motion along a linear path in a given direction.

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