# Which Speed Calculation Method Is Best: DV/DR or V/R?

• anmolnanda
In summary, the conversation discusses the appropriate quantities to use when finding speed in different cases. It is pointed out that both dv/dr and v/r cannot be used in all cases. For constant speeds, v = S/T can be used, while for non-constant speeds, ds/dt at a specific time is used. The appropriateness of using v/r depends on whether v and r represent distance and time or velocity and displacement, particularly when dealing with angular velocity. The conversation also serves as a reminder for clear and complete communication to avoid confusion and receive well-thought out responses.
anmolnanda
in some cases we use dv/dr to find speed and in some cases we use v/r which 1 will be more appropriate to use?

anmolnanda said:
in some cases we use dv/dr to find speed and in some cases we use v/r which 1 will be more appropriate to use?

Er.. you can't use either one!

Speed, or velocity, is defined as ds/dt, where s is displacement. If speed is constant, then finding the total net displacement S, over a period of time T, will give you v = S/T (for v constant). If v isn't constant, then the instantaneous you use ds/dt at a particular time t.

Zz.

What are v and r? If they are distance and time , then dv/dr is the appropriate quantity. v/r will work for constant velocities only.
However if v and r represent velocity and displacement and you are talking about angular velocity then v/r is the correct quantity.

Very good point.

Consider this as a lesson, especially to new members, that if you neglect to present your question clearly and completely, you'll not only cause confusion, but also get confusing responses. If you wish that people who respond to your queries put in some effort and thought into presenting a response that is clear and well-thought out, then it is imperative that YOU do the same as well!

Zz.

I would say that the appropriate method for finding speed depends on the specific situation and the variables involved. Both dv/dr and v/r are valid methods for finding speed, but they may be more suitable for different scenarios.

In general, dv/dr (change in distance over change in time) is more suitable for situations where the speed is changing over time. This can be seen in cases where an object is accelerating or decelerating, as the speed is not constant and therefore cannot be accurately measured using v/r (velocity over radius). For example, in a car race, where the cars are constantly changing their speed, using dv/dr would be more appropriate.

On the other hand, v/r may be more appropriate for situations where the speed is constant, such as in circular motion. In this case, the radius remains the same, so using v/r would provide an accurate measurement of the speed. Another example would be a rotating fan, where the speed of the blades remains constant and can be measured using v/r.

In conclusion, both methods have their own strengths and limitations, and the appropriate method to use for finding speed will depend on the specific circumstances of the situation. As a scientist, it is important to carefully consider the variables involved and choose the most appropriate method for accurate and reliable results.

## 1. What is the difference between DV/DR and V/R when finding speed?

DV/DR and V/R are two different methods used to calculate speed. DV/DR stands for distance divided by time, while V/R stands for velocity divided by rate. While both methods can be used to find speed, DV/DR is used for constant speed situations while V/R is used for changing speed situations.

## 2. How do you calculate speed using DV/DR?

To calculate speed using DV/DR, you need to know the distance traveled and the time it took to travel that distance. Simply divide the distance by the time to get the speed in units of distance per time (e.g. miles per hour).

## 3. How do you calculate speed using V/R?

To calculate speed using V/R, you need to know the velocity (speed and direction) and the rate of change. Simply divide the velocity by the rate of change to get the speed in units of velocity per rate of change (e.g. meters per second per second).

## 4. Which method should I use to find speed?

The method you should use depends on the situation. If the speed is constant, use DV/DR. If the speed is changing, use V/R. It's important to understand the concept and choose the appropriate method to get an accurate calculation.

## 5. Can I use both methods to find speed in the same situation?

Yes, you can use both methods in the same situation to verify your results. However, it's important to understand when to use each method and know which one is more appropriate for the given situation. It's also important to ensure that your units are consistent when using both methods.

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