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What Is Speed In Physics

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What is speed and velocity in physics?

Speed and velocity both measure an objects rate of motion. However, speed is a scalar quantity, which means that it can be described with a numerical value. Velocity is a vector quantity, which depends on direction as well as magnitude. Read these definition for more information:

  • speed – the rate of distance traveled by a moving object over time
  • velocity – the rate of displacement of a moving object over time

Basically, an objects speed tells you how fast its going. Its velocity tells you how fast its going in a certain direction. You use speed measurements in your daily life, but physicists depend on velocity measurements more frequently in their work.

What Is The Most Economical Driving Speed

While the most economical driving speed changes with every vehicle, the general consensus is that it is around 50 mph . There are a few other things you can do to maximise efficiency, however. First, try to maintain a constant speed, this will make your engine run as efficiently as possible – use cruise control on flats if you have it. Second, drive at the highest possible gear within the speed limit, this again helps your engine run as economically as possible. Other tips include turning off AC and having as little weight in your car as you can.

What Is A Light

A light-year is the distance that light can travel in one year about 6 trillion miles . It’s one way that astronomers and physicists measure immense distances across our universe.

Light travels from the moon to our eyes in about 1 second, which means the moon is about 1 light-second away. Sunlight takes about 8 minutes to reach our eyes, so the sun is about 8 light-minutes away. Light from Alpha Centauri, which is the nearest star system to our own, requires roughly 4.3 years to get here, so Alpha Centauri is 4.3 light-years away.

“To obtain an idea of the size of a light-year, take the circumference of the Earth , lay it out in a straight line, multiply the length of the line by 7.5 , then place 31.6 million similar lines end to end,” said NASA’s Glenn Research Center. “The resulting distance is almost 6 trillion miles!”

Stars and other objects beyond our solar system lie anywhere from a few light-years to a few billion light-years away. And everything astronomers “see” in the distant universe is literally history. When astronomers study objects that are far away, the objects appear as they existed at the time that light left them.

Related: Why the universe is all history

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Difference Between Speed And Velocity

Speed denotes only how fast an object is moving, whereas velocity describes both how fast and in which direction the object is moving. If a car is said to travel at 60 km/h, its speed has been specified. However, if the car is said to move at 60 km/h to the north, its velocity has now been specified.

The big difference can be discerned when considering movement around a circle. When something moves in a circular path and returns to its starting point, its average velocity is zero, but its average speed is found by dividing the circumference of the circle by the time taken to move around the circle. This is because the average velocity is calculated by considering only the displacement between the starting and end points, whereas the average speed considers only the total distance travelled.

Finding The Dimensional Formula Of Speed

Average Speed

The mathematical representation of speed is:\Dimensional formula of Distance = M0L1T0Dimensional formula of time = M0L0T1Dividing the dimensional formula of distance by the dimensional formula of time, we get:\Therefore, the dimensional formula of speed =


There are four types of speed and they are:

  • Uniform speed
  • Average speed
  • Instantaneous speed

Uniform speed: A object is said to be in uniform speed when the object covers equal distance in equal time intervals.

Variable speed: A object is said to be in variable speed when the object covers a different distance at equal intervals of times.

Average speed: Average speed is defined as the uniform speed which is given by the ratio of total distance travelled by an object to the total time taken by the object.

Instantaneous speed: When an object is moving with variable speed, then the speed of that object at any instant of time is known as instantaneous speed.

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Related Questions And Answers

Why retardation is called negative acceleration?

What is the meaning of uniform acceleration?

Why does acceleration stay constant?

What’s an example of constant speed?

What change speed means?

How is speed used in everyday life?

Can the speed of a body be negative?

What causes acceleration?

What is the acceleration of a body?

Can a body have uniform speed but still have acceleration?

What is the acceleration of a body moving with uniform speed?

What is acceleration and its type?

How fast are we going?

Selected Solutions To Problems & Exercises

1. 0.288 m

3. 332 m/s

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7. 0.223

9. 7.70 m This means that sonar is good for spotting and locating large objects, but it isnt able to resolve smaller objects, or detect the detailed shapes of objects. Objects like ships or large pieces of airplanes can be found by sonar, while smaller pieces must be found by other means.

11. 18.0 ms, 17.1 ms 5.00% This uncertainty could definitely cause difficulties for the bat, if it didnt continue to use sound as it closed in on its prey. A 5% uncertainty could be the difference between catching the prey around the neck or around the chest, which means that it could miss grabbing its prey.

  • College Physics. : OpenStax College. Located at: . License: CC BY: Attribution. License Terms: Located at License

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Why We Still Love The Idea Of Faster

Science fiction loves the idea of “warp speed.” Faster-than-light travel makes countless sci-fi franchises possible, condensing the vast expanses of space and letting characters pop back and forth between star systems with ease.

But while faster-than-light travel isn’t guaranteed impossible, we’d need to harness some pretty exotic physics to make it work. Luckily for sci-fi enthusiasts and theoretical physicists alike, there are lots of avenues to explore.

All we have to do is figure out how to not move ourselves since special relativity would ensure we’d be long destroyed before we reached high enough speed but instead, move the space around us. Easy, right?

One proposed idea involves a spaceship that could fold a space-time bubble around itself. Sounds great, both in theory and in fiction.

Related: Spaceship could fly faster than light

“If Captain Kirk were constrained to move at the speed of our fastest rockets, it would take him a hundred thousand years just to get to the next star system,” said Seth Shostak, an astronomer at the Search for Extraterrestrial Intelligence Institute in Mountain View, California, in a 2010 interview with’s sister site LiveScience. “So science fiction has long postulated a way to beat the speed of light barrier so the story can move a little more quickly.”

How Fast Am I Going

What is Velocity? | Physics | Don’t Memorise

Speed is not a precise term – there are a few more accurate meanings, and they should not be confused with each other. Let’s consider the differences between instantaneous speed, average speed and rotational speed. For the purpose of two first, we will try to visualize it with an example of driving a car.

You are driving along the long, open highway. You glance down at the speedometer of your car it reads 100 kilometers per hour. From this, you know how far you will drive if you keep the speed constant. We know that, in practice, keeping the speed exactly constant is almost impossible , and our speed fluctuates all the time, more or less. The actual distance you travel in an hour is the average of all these speeds. Conclusion – the average speed is the total distance traveled in a unit of time .

So, what does the number your speedometer indicates really mean? That is your instantaneous speed your speed at this exact moment. According to the textbook definition, the instantaneous speed is the change in object position, x, between two times, tâ and tâ .

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What’s The Difference Between Speed And Velocity

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When describing the motion of objects in terms of distance, time, and direction, physicists use the basic quantities of speed and velocity. Two terms, two distinct meanings. Yet, not uncommonly, we hear these terms used interchangeably. So, whats the difference? Why is it incorrect to use the terms speed and velocity interchangeably?

The reason is simple. Speed is the time rate at which an object is moving along a path, while velocity is the rate and direction of an objects movement. Put another way, speed is a scalar value, while velocity is a vector. For example, 50 km/hr describes the speed at which a car is traveling along a road, while 50 km/hr west describes the velocity at which it is traveling.

The mathematical calculation for speed is relatively straightforward, wherein the average speed of an object is calculated by dividing the distance traveled by the time it took the object to travel the distance. Velocity, on the other hand, is more complicated mathematically and can be calculated in different ways, depending on what information is available about the objects motion. In its simplest form, average velocity is calculated by dividing change in position by change in time .

What Is The Equation For Speed

The most common equation for speed is: speed = distance / time. It can also be expressed as the time derivative of the distance traveled. Mathematically, it can be written as v = s/t, or v = , where speed is denoted by v, distance is denoted by s, and time is denoted by t. In case of uniform velocity, the first equation is used.

Speed is often confused with velocity and is thought to have the same meaning. In terms of physics, speed and velocity are two different things. Speed is a scalar quantity, which means that there is no direction attached with its definition and only represents the magnitude of its velocity. Velocity is a vector quantity and represents both the speed of an object and its direction. For example if a car travels north at 40 miles per hour, then its speed is 40 miles per hour and its velocity is 40 miles per hour to the north.

Speed is associated with the concept of distance, whereas velocity is associated with displacement. Distance, a scalar quantity, represents the length an object has covered during its time of motion. Displacement, a vector quantity, represents how far the object has moved away from its initial position during its time of motion.

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What Goes Faster Than The Speed Of Light

Although the speed of light is often referred to as the universe’s speed limit, the universe actually expands even faster. The universe expands at a little more than 42 miles per second for each megaparsec of distance from the observer, wrote astrophysicist Paul Sutter in a previous article for

In other words, a galaxy 1 megaparsec away appears to be traveling away from the Milky Way at a speed of 42 miles per second , while a galaxy two megaparsecs away recedes at nearly 86 miles per second , and so on.

“At some point, at some obscene distance, the speed tips over the scales and exceeds the speed of light, all from the natural, regular expansion of space,” Sutter explained. “It seems like it should be illegal, doesn’t it?”

Special relativity provides an absolute speed limit within the universe, according to Sutter, but Einstein’s 1915 theory regarding general relativity allows different behavior when the physics you’re examining are no longer “local.”

“A galaxy on the far side of the universe? That’s the domain of general relativity, and general relativity says: Who cares! That galaxy can have any speed it wants, as long as it stays way far away, and not up next to your face,” Sutter wrote. “Special relativity doesn’t care about the speed superluminal or otherwise of a distant galaxy. And neither should you.”

Is Velocity The Same As Speed

Speed and Velocity (Physics)

Velocity and speed are very nearly the same – in fact the only difference between the two is that velocity is speed with direction. Speed is what is known as a scalar quantity, meaning that it can be described by a single number . It is also the magnitude of velocity. Velocity, a vector quality, must have both the magnitude and direction specified, e.g. travelling 90 mph south east.

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What Is Speed In Physics

We are giving a detailed and clear sheet on all Physics Notes that are very useful to understand the Basic Physics Concepts.

Types of Speed in Physics

Uniform Speed Definition:If an object covers equal distances in equal intervals of time, then its speed is called uniform speed.

Non-uniform Definition or Variable Speed:If an object covers unequal distances in equal intervals of time and vice-versa then its speed is called non-uniform or variable speed.

Average Speed Definition:The ratio of the total distance travelled by the object to the total time taken is called average speed of the object.

If a particle travels distances s1, s2, s3, with speeds v1 v2, v3,., then


If particle travels equal distances with velocities v1 and v2, then


If a particle travels with speeds v1, v2, v3, during time intervals t1, t2, t3, then

If particle travels with speeds v1 and v2 for equal time intervals, i.e. t1 = t2 = t, then

When a body travels equal distance with speeds v1 and v2, the average speed is the harmonic mean of two speeds, i.e.

Instantaneous Speed Definition:When an object is travelling with variable speed, then its speed at a given instant of time is called its instantaneous speed.

Motion in a Straight Line Topics:

Difference Between Uniform And Non Uniform Speed

Uniform Speed:

The body has uniform speed if it covers equal distances in equal intervals of time however short the interval may be.

In the equation, S=v t v is the average speed of a body during time t. It is because the speed of the body may be changing during the time interval t. However, if the speed of a body does not vary and has the same value then the body is said to possess uniform speed.

Non Uniform Speed:

A body does not have uniform speed if it does not cover the equal distance with an equal interval of time.Related Topics:

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Average Vs Instantaneous Speed

The examples so far calculate average speed: how far something travels over a period of time.

But speed can change as time goes by. A car can go faster and slower, maybe even stop at lights.

So there is also instantaneous speed: the speed at an instant in time. We can try to measure it by using a very short span of time .

Time Velocity And Speed

physics – what is speed?
  • Explain the relationships between instantaneous velocity, average velocity, instantaneous speed, average speed, displacement, and time.
  • Calculate velocity and speed given initial position, initial time, final position, and final time.
  • Derive a graph of velocity vs. time given a graph of position vs. time.
  • Interpret a graph of velocity vs. time.

Figure 1. The motion of these racing snails can be described by their speeds and their velocities.

There is more to motion than distance and displacement. Questions such as, How long does a foot race take? and What was the runners speed? cannot be answered without an understanding of other concepts. In this section we add definitions of time, velocity, and speed to expand our description of motion.

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How Did We Learn The Speed Of Light

As early as the 5th century, Greek philosophers like Empedocles and Aristotle disagreed on the nature of light speed. Empedocles thought that light, whatever it was made of, must travel and therefore, must have a rate of travel. Aristotle wrote a rebuttal of Empedocles’ view in his own treatise, On Sense and the Sensible, arguing that light, unlike sound and smell, is instantaneous. Aristotle was wrong, of course, but it would take hundreds of years for anyone to prove it.

In the mid 1600s, recounts PBS NOVA, the Italian astronomer Galileo Galilei stood two people on hills less than a mile apart. Each person held a shielded lantern. One uncovered his lantern when the other person saw the flash, he uncovered his too. But Galileo’s experimental distance wasn’t far enough for his participants to record the speed of light. He could only conclude that light traveled at least 10 times faster than sound.

Rømer used his observations to estimate the speed of light. Since the size of the solar system and Earth’s orbit wasn’t yet accurately known, argued a 1998 paper in the American Journal of Physics, he was a bit off. But at last, scientists had a number to work with. Rømer’s calculation put the speed of light at about 124,000 miles per second .

Though Michelson and Morley built a sophisticated interferometer , Michelson could not find evidence of any kind of luminiferous aether whatsoever. Light, he determined, can and does travel through a vacuum.

What Are The Types Of Speed

Speed has many different types and terms to describe it:

  • Speed – how fast an object is travelling.
  • Velocity – how fast an object is travelling in a certain direction.
  • Acceleration – how quickly it takes an object to reach a certain speed.
  • Constant speed – an object moving at the same rate.
  • Variable speed – an object moving at a changing rate.
  • Average speed – distance covered divided by time taken to traverse.
  • Instantaneous speed – the speed at a particular instance.

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