Motion, Speed, Velocity and Acceleration

Biola Emmanuel - Thu, 27th June, 2019 @ 14:48: PM

Topics in Physics

Newton Laws of Motion Motion, Speed, Velocity and Acceleration Heat Transfer, Conduction, Convection and Radiation Concept of Heat and Temperature Gravity explained with some fun facts Zeroth Law of Thermodynamics Fundamental and Derived units Important Physics Concepts

Academic Questions in Physics

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Consider this expression below:

A body X exerts a force FX on another body Y. In return, body Y exert a force FY back on body X. The forces FX and FY are equal in magnitude but opposite in direction.

Putting the above expression into equation:

FA = -FB

Where FA is the action force

FB is the reaction Force

The above expression relates to _____.

  • A. Theory of Force
  • B. Force Postulate
  • C. Einstein's proposal on Relativity
  • D. Newton's 1st law of motion
  • E. Newton's 2nd law of motion
  • F. Newton's 3rd law of motion

The tendency of a body to remain in a state of rest or in uniform motion is referred to as _____.

  • A. tension
  • B. uniform acceleration
  • C. constant acceleration
  • D. deceleration
  • E. inertia
  • F. velocity

A change in the position of an object with reference to time is best described as _____.

  • A. momentum
  • B. displacement
  • C. velocity
  • D. acceleration
  • E. direction
  • F. motion

The saying "what goes up on earth must come down" can be best attributed to _____.

  • A. force
  • B. motion
  • C. mass
  • D. acceleration
  • E. average velocity
  • F. constant velocity

We have _____ laws of Thermodynamics.

  • A. 1
  • B. 2
  • C. 3
  • D. 4
  • E. 5
  • D. 6


Motion happens to be one of the interesting topics in physics and is said to occur when something moves. We live in a universe where everything moves, although at a different rate. For instance:

  • The earth orbits or revolves round the sun
  • The moon revolves round the earth (as earth’s satellite)

You may read on the solar system here.


In physics, motion refers to a change in the position of an object with reference to time.

Although we may sometimes sit or stand in a fixed position, that doesn’t mean motion isn’t taking place. The fact that the earth is rotating implies that we are indirectly moving along with it.

We can thus say that motion can be relative to some frame of reference.

In the above instance, the earth (constantly rotating along its axis) is our frame of reference and everything present on earth is in motion with regard to earth as a frame of reference. Another instance will be someone sitting on a moving bus. The person will appear not to be moving but since the bus is in motion, we can conclude that the motion of the person sitting inside the bus is relative to the bus.

Force is responsible for the motion/movements present the universe. For an object to move, a force must act on it. For instance, if we keep a pin in a vacuum and it’s left untouched, the pin will remain in that position forever unless it is acted upon by a force. This force could be in the form of an applied air or a deliberate touch by humans.


In order to get a better understanding of motion, it is important we know how the following terms work since they all involved in motion. The terms are:

1. Speed

Speed is simply the rate of motion since it is a measure of how fast or slow an object is moving. The dimensions associated with speed are distance and time. For instance, if one covers a distance of 10000 meters in 50 seconds and another covers the same distance in 5000 seconds, we can conclude that the first person has a faster speed than the second person because he covered the same distance at a lesser time.

Speed is defined as distance travelled per unit of time OR the rate of change of distance

Speed = distance/Time

Note: Distance is total length of path travelled from one point to another. It is measured in meters.

Time is a duration or period during which things happen. It is measured in seconds.

Speed is a scalar quantity since it is has only magnitude (measured only in numerical value)


2. Velocity

Although velocity and speed may be used interchangeably by students and even teachers, they are NOT the same thing. The direction in which an object is moving is what differentiates velocity from speed.

Velocity can be defined as speed in a given direction OR the rate of change of displacement.

It is a vector quantity because it has magnitude and direction

Velocity = Change in distance/Change in time

The statement below differentiates speed from velocity.

A bus is moving on a highway at a speed of 100 meters per 20 seconds. When the bus changes its direction and moves at a different speed (or even the same speed), that’s velocity. For instance, the bus may move at a velocity of 100m/20s in the northern direction and 200m/20s in the eastern direction.

Note: Speed and velocity both have the same Standard International unit which is meter per second (m/s)


3. Acceleration

The velocity of a moving object can either decrease or increase over a period of time; and this is where acceleration comes into play. For instance when you ride a bicycle, you start slowly but as soon as you increase the push on the pedals, the bicycle moves faster (accelerate). When you stop pushing the pedals, the bicycle begins to move slowly (negative acceleration).

From the above, we can therefore say that acceleration can also be negative.

Note: Deceleration is an English term used to describe negative acceleration but in physics, we use the term acceleration to denote both the positive and negative changes in velocity.

Acceleration can be defined as the rate of change of velocity OR the measurement of how much the velocity of an object changes with time.

Acceleration = Change in velocity/Change in time

If an object changes velocity after a fixed amount of time, then such acceleration is called constant acceleration. Take for instance, when we throw a table tennis ball on a slope, it will roll downwards more rapidly at each second. On the 1st second its velocity could be 20m/s, on the 2nd second, its velocity becomes 25m/s and on the 3rd second, it becomes 30m/s and so on. Such ball can be said to have a constant acceleration of 5m/s. (That is, for every 5 meters moved, the tennis ball accelerates by one second).

Average acceleration is the total change in velocity over a period of time, divided by the duration of that period.

Note: Acceleration is a vector quantity and its Standard International unit (SI unit) is meter per second (m/s) or meter per second square (m/s2)

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Amazing facts in Physics

Every planet has its own unique gravitational force, for instance, Mars has a gravity of 3.711 m/s2 while earth’s gravitational force is 9.807m/s2Please read on gravity here

When two metals are put together in space, they will stick together as if they are welded. This phenomenon is called cold welding


Physics is one of the core sciences.

Physics is defined the scientific study of matter and the movement of matter through the space and time of the universe.

Understanding the basic and fundamental concepts of physics will help you better comprehend this subject. Below are some of the concepts:

  1. The Laws of Motion (Classical Mechanics)
  2. Electromagnetism
  3. Relativity
  4. Thermodynamics

Please read on the basic introduction of the above physics concept here