Must two quantities have the same dimensions

In summary, the conversation discusses the requirement for two quantities to have the same dimensions when using one quantity as an exponent in raising the other to a power. The dimension of '2' in mv2/r is also questioned, with the simple answer being that v2 means v times v. It is mentioned that the exponent must be dimensionless, and the argument for certain functions such as sin, cos, or log must also be dimensionless. The concept of (velocity)2 is discussed, and it is compared to other examples such as (length)2 and (length)3. The idea of acceleration (meters / sec2) is also explained as (meters per second) per second.
  • #1
Nikhil faraday
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Must two quantities have the same dimensions if you are using one quantity as an exponent in raising other to a power?
What is the dimension ( or dimensionless) of '2' in mv2/r ?( v is raised to the second power)
 
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  • #2
The exponent should be dimensionless. The simple answer is: v2 means v times v.
 
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Likes sophiecentaur and Chestermiller
  • #3
Nikhil faraday said:
Must two quantities have the same dimensions if you are using one quantity as an exponent in raising other to a power?
To second what @scottdave said, the exponent must be dimensionless. Also the argument to a sin or cos or other trig function or a log must all be dimensionless.
 
  • #4
I admit that it is difficult to think of what (velocity)2 could mean. (Length)2 is easy enough to understand that is Area. (length)3is volume.
Even Acceleration (meters / sec2) might at first seem baffling, but you can rewrite it as (meters per second) per second.

Think of it like this: 9.8 meters per second per second. What does it mean? Every second, a falling object gains another 9.8 m/s of velocity.
 

1. What are dimensions in science?

Dimensions in science refer to the physical units or measurements used to describe a quantity, such as length, time, mass, or temperature. These dimensions are typically represented using standard units, such as meters, seconds, kilograms, or degrees Celsius.

2. Why must two quantities have the same dimensions?

In order for two quantities to be compared or combined in a meaningful way, they must have the same dimensions. This is because quantities with different dimensions cannot be added, subtracted, multiplied, or divided. In other words, the dimensions must be consistent for calculations to be valid.

3. What happens if two quantities with different dimensions are added together?

If two quantities with different dimensions are added together, the result will be a nonsensical value. For example, adding 5 meters to 10 seconds would result in 15 meters-seconds, which does not have a real-world meaning. This is why it is important for quantities to have the same dimensions when performing calculations.

4. Are dimensions always the same for a given quantity?

No, dimensions can vary depending on the system of units used. For example, length can be measured in meters, feet, or inches, and each will have a different numerical value. However, the dimensions will always be the same - in this case, length - regardless of the unit used.

5. Can dimensions be converted between different units?

Yes, dimensions can be converted between different units as long as they are the same type of measurement. For example, length can be converted from meters to centimeters by multiplying by 100. However, dimensions cannot be converted between different types of measurements, such as length and time.

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