Because the person always returns to the original position, the motion would never result in a change in position. Since velocity is defined as the rate at which the position changes, this motion results in zero velocity. If a person in motion wishes to maximize their velocity, then that person must make every effort to maximize the amount that they are displaced from their original position.
Every step must go into moving that person further from where he or she started. For certain, the person should never change directions and begin to return to the starting position. Velocity is a vector quantity. As such, velocity is direction aware. When evaluating the velocity of an object, one must keep track of direction. One must include direction information in order to fully describe the velocity of the object. This is one of the essential differences between speed and velocity.
Speed is a scalar quantity and does not keep track of direction ; velocity is a vector quantity and is direction aware. The task of describing the direction of the velocity vector is easy. The direction of the velocity vector is simply the same as the direction that an object is moving. It would not matter whether the object is speeding up or slowing down. If an object is moving rightwards, then its velocity is described as being rightwards.
If an object is moving downwards, then its velocity is described as being downwards. Note that speed has no direction it is a scalar and the velocity at any instant is simply the speed value with a direction. Let's begin implementing our understanding of these formulas with the following problem:. Q: While on vacation, Lisa Carr traveled a total distance of miles. Her trip took 8 hours.
What was her average speed? That was easy! Lisa Carr averaged a speed of 55 miles per hour. Yet, she averaged a speed of 55 miles per hour.
The above formula represents a shortcut method of determining the average speed of an object. Since a moving object often changes its speed during its motion, it is common to distinguish between the average speed and the instantaneous speed. Measure ad performance.
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Cite this Article Format. Jones, Andrew Zimmerman. The symbol v is used for speed because of the association between speed and velocity, which will be discussed shortly. Don't like symbols? Well then, here's another way to define speed. Speed is the rate of change of distance with time. In order to calculate the speed of an object we must know how far it's gone and how long it took to get there. Let's say you drove a car from New York to Boston.
The distance by road is roughly km miles. If the trip takes four hours, what was your speed? Applying the formula above gives…. This is the answer the equation gives us, but how right is it?
Was 75 kph the speed of the car? Yes, of course it was… Well, maybe, I guess… No, it couldn't have been the speed. Unless you live in a world where cars have some kind of exceptional cruise control and traffic flows in some ideal manner, your speed during this hypothetical journey must certainly have varied. Thus, the number calculated above is not the speed of the car, it's the average speed for the entire journey. In order to emphasize this point, the equation is sometimes modified as follows….
Read it as "vee bar is delta ess over delta tee". This is the quantity we calculated for our hypothetical trip. In contrast, a car's speedometer shows its instantaneous speed , that is, the speed determined over a very small interval of time — an instant.
Ideally this interval should be as close to zero as possible, but in reality we are limited by the sensitivity of our measuring devices.
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