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How To Calculate Average Speed In Physics

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What Is Average Velocity

Calculating average velocity or speed | One-dimensional motion | Physics | Khan Academy

Average velocity is a vector quantity. Average velocity is defined as the change in position or displacement divided by the time intervals in which the displacement occurs.The average velocity can be positive or negative depending upon the sign of the displacement. The SI unit of average velocity is meters per second .

Whats The Difference Between Mph And Kph

Kilometers per hour has an abbreviation of kph and it refers to the number of kilometers a given object traveled in one hour. Conversely, miles per hour has an abbreviation of mph and it refers to the number of miles a given object traveled in one hour. Both are units of measurements used for speed.

If you want to convert an mph value to a kph value, take the mph value and multiply this by 1.61. On the contrary, if you want to convert a kph value to an mph value, take the kph value and multiply this by 0.61. This is because:

1 mile = 1.61 kilometers, and 1 kilometer = 0.061 miles

You can breakdown both mph and kph into meters per second and feet per second. For kph, all you have to do is multiply the total speed by 1,000 then divide the value you get by 3,600. For mph, all you have to do is multiply the total speed by 5,280 then divide the value you get by 3,600.

The main difference between these two units of measurement is one is from the metric system while the other is from the US customary system.

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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What Is The Unit For Speed

The unit for speed is distance over time, as it is defined as the amount of time it takes an object to cover a particular distance. The base, or SI, unit is metres per second, but this is not very practical in everyday life. You are likely more familiar with units such as kilometres per hour, miles per hour and knots. Any distance over time is a speed unit, so other units of speed include nanometres per fortnight, Boeing 787s per solar year, or bananas per Friedman.

Differences Between Speed And Velocity

Average speed formula

The differences between speed and velocity can be summarised as:


4. no dependence on direction and so is only positive

4. direction can be determined from the sign convention used

Additionally, an object that makes a round trip, i.e. travels away from its starting point and then returns to the same point has zero velocity but travels at a non-zero speed.

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Formula Of Average Speed

The formula for average speed is found by calculating the ratio of the total distance traveled by the body to the time taken to cover that distance.

The average speed equation is articulated as:

Total Distance traveled/Total Time taken

Equation is the formula for an average speed of an object moving at a varying speed.

Finding Average Speed Examples

Example 1: Using the equation above, find the speed of a train which travelled 120 miles in 2 hours and 10 minutes while making four stops, each lasting approximately 2.5 minutes. First, subtract the time spent at the train stops: 2.5 x 4 = 10 minutes. 2:10 minus 10 minutes leaves 2 hours of travel time. Then, apply the avg speed formula to get 120 miles / 2 hours = 60 mph .

Example 2: A cyclist travels to and from work, covering 10 km each way. It took him 25 minutes on the way to work and 35 minutes on the way back. What is the cyclist’s average speed? First, add up the time to get 1 hour total. Also add up the distance: 5 + 5 = 10 kilometers. Finally, replace in the formula to get 10 / 1 = 10 km/h on average in total.

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How To Calculate Average Velocity

This article was co-authored by wikiHow staff writer, Hannah Madden. Hannah Madden is a writer, editor, and artist currently living in Portland, Oregon. In 2018, she graduated from Portland State University with a B.S. in Environmental Studies. Hannah enjoys writing articles about conservation, sustainability, and eco-friendly products. When she isnt writing, you can find Hannah working on hand embroidery projects and listening to music.There are 8 references cited in this article, which can be found at the bottom of the page. This article has been viewed 688,985 times.Learn more…

All you need to calculate average velocity is the total displacement, or change in position, and the total time. Remember that velocity measures direction as well as speed, so include the direction in your answer, such as “north,” “forward,” or “left.” If the problem involves constant acceleration, you can learn a shortcut that will make finding the solution even easier.

Average Speed Formula And Examples: Distance Displacement

Physics: Kinematics: Calculating Average Speed

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Average speed and speed are not the same though they are calculated using the same formula. Average speed is the mean value of speed with which any person or object covers the entire distance from source to destination. You may have noticed it is very difficult to maintain a constant speed when you are driving, running, or walking there is a high rate of fluctuation by doing any of this activity.

Table of Content

Key Terms: Distance, Displacement, Speed, Velocity, Odometer, Vector Quantity

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Examples On Average Speed Formula

Let us take a look at a few examples to better understand the formula for average speed.

Example 1: Using the average speed formula, find the average speed of Sam, who covers the first 200 kilometers in 4 hours and the next 160 kilometers in another 4 hours.


To find the average speed we need the total distance and the total time.Total distance covered by Sam = 200Km + 160 km = 360 kmTotal time taken by Sam = 4 hour + 4 hour = 8 hourAverage Speed = Total distance covered ÷ Total time takenAverage Speed = 360 ÷ 8 = 45km/hr

Answer: Average speed of Sam is 45 km/hr.

Example 2: A train is moving with a speed of 80 miles per hour for the first 4 hours and 110 miles per hour for the next 3 hours. Find the average speed of the train with the help of the average speed formula.


It is given that the train is moving at a speed of 80 miles per hour for the first 4 hours.Here \ = 80 and \ = 4.And the train is moving at a speed of 110 miles per hour for the next 3 hours.Hence \ = 110 and \ = 3.Average Speed Formula = \Average Speed = ÷ = ÷ = 92.86 miles/hour

Answer: The average speed of the train is 92.86 miles/hour.

Example 3: A car travels at a speed of 45 km/hr for 5 hours and then decides to slow down to 40 km/hr for the next 2 hours. Calculate the average speed using the average speed formula.


Answer: Average speed of a car is 43.57 m/s.

How Can I Calculate Average

Average equals the sum of a set of numbers divided by the count which is the number of the values being added. For example say you want the average of 13 54 88 27 and 104. Find the sum of the numbers: 13 + 54 + 88+ 27 + 104 = 286. There are five numbers in our data set so divide 286 by 5 to get 57.2.

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Displacement And Related Quantities

Bongani has to walk to the shop to buy some milk. After walking \ \, he realises that he does not have enough money, and goes back home. If it took him two minutes to leave and come back, calculate the following:

  • How long was he out of the house in seconds)?

  • How far did he walk )?

  • What was his displacement )?

  • What was his average velocity )?

  • What was his average speed )?

  • Bridget is watching a straight stretch of road from her classroom window. She can see two poles which she earlier measured to be \ \ apart. Using her stopwatch, Bridget notices that it takes \ \ for most cars to travel from the one pole to the other.

  • Using the equation for velocity \\), show all the working needed to calculate the velocity of a car travelling from the left to the right.

  • If Bridget measures the velocity of a red Golf to be \ \, in which direction was the Golf travelling?

  • Bridget leaves her stopwatch running, and notices that at \, a taxi passes the left pole at the same time as a bus passes the right pole. At time \ the taxi passes the right pole. At time \, the bus passes the left pole.

    How long did it take the taxi and the bus to travel the distance between the poles?

  • What was the average velocity of the taxi and the bus?

  • What was the average speed of the taxi and the bus?

  • What was the average speed of taxi and the bus in \?

  • A rabbit runs across a freeway. There is a car, \ \ away travelling towards the rabbit.

  • If the car is travelling at \ \, what is the car’s speed in \.

  • The Formula For Average Speed And Average Velocity

    Formula For Velocity 5th Grade

    If x is the displacement of an object in time t, then:

    The formula for average speed is given as:

    vav = x/t

    You noticed that the formula for average velocity and average speed is the same.

    The only difference lies in the type of physical quantity, i.e., speed and velocity. Speed is a scalar quantity that has magnitude only. However, velocity is a vector quantity that has both magnitude and direction.

    Now, let us go through some average speed problems:


    1. A car travels a distance of 70 km in 2 hours. What is the average speed?

    Answer: average speed = distance/time

    Therefore, the average speed of the car is 70 km/2 hours = 35km/hour.

    2. A person can walk at a speed of 1.5 meters/second. How far will he walk in 4 minutes?

    Answer: average speed = distance/time

    Distance = average speed

    = 1.5 = 360 meters

    3. A train travels in a straight line at a constant speed of 60 km/h for a particular distance d and then travels another distance equal to 2d in the same direction at a constant speed of 80 km/h in the same direction as it was previously going. a) What is the average speed of the train during the whole journey?

    Solution: a) The time t1 to cover distance d at a speed of 60 km/h is given by t1 = d / 60

    The time t2 to cover distance 2d at a speed of 80 km/h is given by t2 = 2d / 80

    Average Speed = distance/time = / +

    = 3d / /

    = 3 d/ = 3d /200d = 72 km/h

    Solution: Initial distance travelled by the person, xi = 7 m,

    Final distance travelled, xf = 18 m,

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    When Is The Average Velocity Zero

    For instance, if a remote-controlled car is racing from Point A to Point B and back to Point A, there is no overall car displacement. In that case, the speed of the car can be measured but not its velocity. If the same car moves from Point A to Point B and stays there, there is definite displacement in a certain direction. It can be measured in such cases. In simpler words, average velocity is just the average speed with a direction. If a trip starts and ends at the same point, the total displacement is zero, so the average velocity is zero.

    Here is a video that provides a detailed explanation of average speed and average velocity with animations!

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    How Fast Am I Going

    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 Is The Most Economical Driving Speed

    While the most economical driving speed changes with every vehicle, the general consensus is thatit 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.

    Problems Related To Both Average Speed And Average Velocity

    Average Speed Calculation – GCSE Physics – Formula

    1. A car travels along a straight road to the east for 120 meters in 5 seconds, then goes west for 60 meters in 1 second. Determine average speed and average velocity.


    Distance = 120 meters + 60 meters = 180 meters

    Displacement = 120 meters 60 meters = 60 meters, to east.

    Time elapsed = 5 seconds + 1 second = 6 seconds.

    Average speed = Distance / time elapsed = 180 meters / 6 seconds = 30 meters/second.

    Average velocity = Displacement / time elapsed = 60 meters / 6 seconds = 10 meters/second.

    2. A runner is running around a rectangle track with length = 50 meters and width = 20 meters. He travels around the rectangle track twice, finally running back to the starting point. If the total time he takes to run around the track is 100 seconds, determine average speed and average velocity.


    The circumference of the rectangle, which is the distance travelled in one round = 2 + 2 = 100 meters + 40 meters = 140 meters.

    When a runner runs around the rectangle twice = 2 = 280 meters.

    Distance = 280 meter

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    Average Speed Solved Examples

    Problem 1: A runner sprints at a track meet. He completes a 1000-meter lap in 1 minute 30 sec. After the finish, he is at the starting point. Calculate the average speed of the runner during this lap?Answer:

    Total distance covered by the runner = 1000 meters

    Total time taken =1minute 30 sec

    = 90 secSo, applying the formula for the average speedwe have,


    11.1 m/s

    Problem 2: A car travels at a speed of 40 km/hr for 2 hours and then decides to slow down to 30 km/hr for the next 2 hours. What is the average speed?Answer:D1 = 40 * 2 = 80 miles

    D2 = 30 * 2 = 60 miles

    Total distance D= D1+D2

    D = 80 + 60

    Total Distance travelled/Total Time taken

    = 140/4

    Read more:Average velocity

    See the video below, to have a clear idea about average speed, average speed formula, and average velocity.

    Hope you learned the average speed definition, average speed formula, how to calculate average speed along with examples. Stay tuned with BYJUS to know more.

    Time Velocity And 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.

    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 To Calculate The Average Speed Of A Car

    Let us say that you travelled a certain distance with your car and want to calculate its average speed. The easiest way to do that would be by using the speed calculator above, but if you prefer, you can also do the math yourself. Either way, one needs to know the distance. If you have noted the distance on your odometer then you can use that number. Other options are to use a map and measure the distance travelled based on your actual path , or to use a GPS reading if you used navigation during the whole trip. Then you need to know the travel time. Make sure to subtract any rests or stops made from the total trip duration.

    For example, if the total distance travelled was 250 miles and the time it took was 5 hours, then the average speed was 250 / 5 = 50 miles per hour . If the distance was 200 kilometers and it took 4 hours to cover it, then the speed was 200 / 4 = 50 km/h .

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