What is Average speed: Definition and 202 Discussions

In everyday use and in kinematics, the speed (commonly referred to as v) of an object is the magnitude of the rate of change of its position with time or the magnitude of the change of its position per unit of time; it is thus a scalar quantity. The average speed of an object in an interval of time is the distance travelled by the object divided by the duration of the interval; the instantaneous speed is the limit of the average speed as the duration of the time interval approaches zero.
Speed has the dimensions of distance divided by time. The SI unit of speed is the metre per second (m/s), but the most common unit of speed in everyday usage is the kilometre per hour (km/h) or, in the US and the UK, miles per hour (mph). For air and marine travel the knot is commonly used.
The fastest possible speed at which energy or information can travel, according to special relativity, is the speed of light in a vacuum c = 299792458 metres per second (approximately 1079000000 km/h or 671000000 mph). Matter cannot quite reach the speed of light, as this would require an infinite amount of energy. In relativity physics, the concept of rapidity replaces the classical idea of speed.

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  1. S

    What is the average speed at a given latitude due to Earth's rotation?

    Homework Statement Any person on the Earth is carried in a cirular path as the Earth rotates on axis. The Earth revolves once in a day. At a latitude of Φ, the distance to the axis of rotation is R = REarthcos(Φ). If Anytown's latitude is 48.8 degrees and the Earth's radius is 6378 km, what is...
  2. J

    Magnitude of average velocity and average speed

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  3. M

    Average speed and average velocity

    Homework Statement The space shuttle takes off from Cape Canaveral in Florida and orbits Earth 18 times before landing back at Cape Canaveral 23 hours and 7 minutes later. During this time, it moves in circular orbit with radius 6.6 x10^6 m. Homework Equations The equation that I am...
  4. S

    What Is the Minimum Average Speed Required to Catch the Ball?

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  5. N

    Calculating Average Speed from Lap 1 & 2

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  6. H

    How long is the bus trip from Balamb to Galbadia?

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  7. R

    Average speed relative to the magnitude of the average velocity?

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  8. C

    How Do You Calculate Average Speed If You're Given Distance and Time in Minutes?

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  9. B

    Speed/dist./time problem (need to find average speed)

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  10. B

    Word problem d=rt, find average speed

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  11. R

    What is the Average Speed for a Car Trip with Different Constant Speeds?

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  12. R

    Average speed vs average velocity

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  13. C

    Displacement, Elapsed Time, Magnitude, Direction, and Average Speed on a Trip.

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  14. C

    How Do You Calculate Average Speed with Variable Speeds and Distances?

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  15. J

    Solve for Average Speed: Jogging and Driving Distance Calculation

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  16. J

    Average Speed Help: Get to Church On Time!

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  17. matt_crouch

    Calculating the average speed of molecules in a gas

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  18. A

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  19. V

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  20. P

    Average speed of the gasoline as it leaves the nozzle?

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  21. G

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  22. L

    Finding average speed & distance traveled?

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  23. M

    How Do You Calculate Average Speed Over Different Speeds?

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  24. S

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  25. B

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  26. P

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  27. T

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  28. T

    Calculating Average Speed of a Car Round Trip

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  29. S

    Word problem: Asking to solve for average velocity and average speed

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  30. S

    Average Speed and Average Velocity Question

    [b]1. To get to a concert in time, a harpsichordist has to drive 124 miles in 2.01 hours. (a) If he drove at an average speed of 53.0 mi/h in a due west direction for the first 1.18 h, what must be his average speed if he is heading 30.0° south of west for the remaining 49.8 min? (b)...
  31. X

    Average speed problem What am I missing?

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  32. B

    Calculating Average Speed: Meeting Your Travel Goal in AP Phys B | 113 km/h

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  33. E

    Challenge: superluminal average speed

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  34. M

    Why Is the Average Speed Not Simply the Arithmetic Mean of Two Speeds?

    I just wanted to know how to find average speed without knowing the distance. I know average speed is defined as total distance / change in time but what would you do a person travels to a friend's house and when he is halfway there, he figures out that he has been averaging 30 mph. He drives...
  35. C

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  36. A

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    obviously the root-means-square speed value is greater than the average value. Question is to why the root-mean-square speed is taken as a kind of average speed for gases but formula used in statistic in getting average number ? As when the number is squared, the final average value is...
  37. R

    Average Speed = distance/time question.

    Homework Statement A race car races on a circular racetrack of radius (r). (a) Write an equation for the car’s average speed when it travels a complete lap in time (t). (b) The radius of the track is 400m and the time to make a lap is 40s. Show that the average speed around the track is 63m/s...
  38. K

    Average Speed - isn't this average velocity?

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  39. S

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    Homework Statement A car is making a trip of 40 mi. It travels half the distance at an average speed of 20 mph. In order for it to have an average speed of 40 mph for the whole trip, the car would need to: a. travel at an average speed of 40 mph for the trip’s remainder. b. travel at an...
  40. F

    Calculate DeltaR RMS for Air Molecule After 5s

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  41. M

    Is there a difference between mean speed and average speed ?

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  42. L

    Homework problem: Average speed and time

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  43. N

    Calculating Average Speed for a Trip: A Physics Challenge

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  44. R

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  45. M

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  46. N

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    A car travels 50km at 30degrees North of East for 20min, then 30km at 70degrees North of East with speed of 20km/hr, then another 10km at 60degrees North of East with speed 80km/hr. Find A)Total distance traveled B)The average speed of the car C)The displacement of the car(magnitude and the...
  47. A

    What Average Speed is Needed for the Car in this Multi-Part Journey Problem?

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  48. X

    Average speed and instantaneous, displacement and distance, speed and velocity

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  49. B

    Average Speed and Force Question

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  50. S

    Finding average speed given two velocities, help

    Homework Statement A person walks first at a constant speed of 47.0m/s along a straight line from point A to point B and then back along the line from B to A at a constant speed of 3.10m/s Homework Equations What is her average speed over the entire trip? The Attempt at a Solution...
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