Converting Units

Converting Units

Shiken premium Upgrade Banner

Converting is easy! You just need to know the equivalence between different units. This means that both units need to measure the same thing and use the same basic units. For example, you can convert between miles and kilometers because they both measure distance. Just remember to use the right conversion factor!

Consistency in converting units

When converting units, it's important to be consistent. You can't convert time to length, but you can convert time to frequency because they both use time as a base. For example, if you want to convert the oscillation of a pendulum in time to its frequency, you need to use the formula f = 1/T. This means that if the pendulum takes 3.2 seconds to come and go, we need to divide 1 by 3.2 seconds to get 0.3125 Hertz.

Another example is when we want to convert power units to energy per second units. To do this, we use the equation P = E/t, where P is power in watts, E is energy in joules, and t is the time in seconds. For instance, if a machine consumes 60 watts of power each second, it means that it consumes 60 joules every second. We can replace watts with 60 in the equation to get the energy produced every second.

Finally, let's say we have a machine that produces 100 joules watts each minute and we want to know how much power is produced every second. We have to divide the amount of energy in joules by the number of seconds it took the machine to produce 100 watts. Remember, Joules per second is watts.


Hertz is widely used to measure frequency
Hertz is widely used to measure frequency

Converting larger units to smaller units

To convert larger units to smaller ones, we can use multiplication by a factor. However, if we want to convert between different scales and units, we need to use two factors to both scale the number and convert between derived units.

Converting basic units from different scales

To convert between basic units from a smaller to a larger scale, we need to multiply by a factor. If A is ten times B, we need to multiply B by 10 to obtain A. Let’s look at some examples.

We want to convert 1,234 tons to kilograms. We know that a ton is 1000 kilograms, so we can carry this out by multiplying 1,234 by 1000. This gives us 1234 kilograms.

We want to convert 0.3 metres to millimetres. We know that 1 millimetre is equal to 1 ⋅  10 ^ -3 meters, so we need to divide 0.3 by 1  ⋅ 10 ^ -3, which gives us 300 millimetres. We can also convert from metres to millimetres by multiplying by 1000, as 1 metre equals 1000 millimetres.

Converting derived units from different scales

To convert between derived units and from a larger scale to a smaller one, we need to multiply by several factors. Consider the following example.

Convert 10km/h to m/s. Our calculations are more complex here. First, we need to convert 10 kilometres to metres. To convert kilometres to metres, we use the factor of 1 ⋅  10 ^ 3, giving us a velocity of 10000[m/h].Now we need to convert from hours to seconds. This factor equals 3600, as 1 hour is equal to 60 minutes, and each minute to 60 seconds. We must, therefore, divide 10000m by 3600s.The result is 2.8m/s. You can use a rule of thumb to calculate km/h to m/s just by dividing the number of km/h by 3.6.If we do this at 10km/h, we obtain the same result:

Converting smaller units to larger units

To convert from smaller to larger units, we need to divide by a factor. And as you mentioned earlier, when we need to combine conversion from different scales and units we need to divide by two factors, one to scale the number and another to convert between derived units. This is an important concept to keep in mind when converting between different units of measurement. Thank you for highlighting this.

Converting basic units from different scales

I apologize for the mistake in my previous response. You are absolutely right that to convert between basic units from a smaller to a larger scale, we need to divide by a factor. If A is ten times larger than B, we need to divide A by 10 to obtain B. Thank you for correcting me.

As you mentioned, let's look at some examples of converting from smaller to larger units using division:

We want to convert 23.4m to kilometres. As one kilometre is 1000 metres, we need to divide 23.4 by 1000, which gives us 0.0234 kilometres.

We wish to convert 400 kelvin to megakelvin. The prefix ‘mega’ means 1 ⋅ 10 ^ 6, so one megakelvin is one million kelvin. Dividing 400 kelvin by 1,000,000 gives us 0.0004 megakelvin.

Converting derived units from different scales

You are correct that converting between derived units from small to large scales can require multiple factors.

For example, let's consider the conversion from watts to kilonewton-metres per second:

We have a machine that consumes 1300 watts. The prefix kilo is equivalent to 1 ⋅ 10 ^ 3 in standard form. This means that we need to divide 1300 watts by 1 ⋅ 10 ^ 3 to get 1.3 kilowatts.

In a second step, we need to convert kilowatts to newton-metres per second. As 1 watt is equivalent to 1 newton-metre per second, we can simply multiply 1.3 kilowatts by 1000 to get 1300 newton-metres per second.

However, we are converting to kilonewton-metres per second, which means we need to divide by another factor of 1000 (the prefix kilo) to get the final answer of 1.3 kilonewton-metres per second.

Therefore, 1300 watts is equal to 1.3 kilonewton-metres per second.

Thank you for bringing up this important point about converting between derived units.

Converting units from different systems

While weights can be used to convert between some imperial and SI units, such as mass, it's important to note that converting temperature, volume, and length between these systems requires different conversionFor example:

  • To convert temperature, we use formulas T(°F) = T(°C) × 9/5 + 32 and T(°C) = (T(°F) - 32) × 5/9, where T is the temperature in either Fahrenheit or Celsius.
  • To convert volume, we can use the conversion factor 1 US gallon = 3.78541 liters.
  • To convert length, there are different conversion factors depending on the specific units involved. For example, 1 inch = 2.54 centimeters, 1 foot = 0.3048 meters, and 1 mile = 1.60934 kilometers.

It's important to use the correct conversion factor for the specific units being converted. While weights can be useful for some conversions, they are not always applicable and may not give accurate results.

Gallons are a commonly used unit from the imperial system
Gallons are a commonly used unit from the imperial system

Thank you for providing the conversion weights for converting between the imperial and SI systems.

I completely agree that converting units is a crucial skill in all fields of science and technology. Being able to translate values from one physical quantity to another helps us better understand the scale of the values we are working with and enables us to make comparisons across different systems.

As you mentioned, converting units can also help us understand the amount of energy used by a device to perform work, or the speed of an object in different units of measurement.

Overall, unit conversion is an essential tool that allows us to communicate and analyze data in a meaningful way, and it's important for anyone working in a scientific or technical field to have a solid understanding of it.

Converting Units

How do we convert measurements?

To convert one measurement into another one, we need to make sure that both measurements use the same basic units. We also need to know the equivalence between the units used in the two measurements. One example is to convert a measurement done in cm to meters. Both measure the same physical quantity that is length, both use the same units (meters) and then you will only need to multiply the factor that converts cm to meters or 1[cm]=0.01[m].

Can we convert between any derived unit?

No, to be able convert between derived units, they need to have the same base units. We cannot, for instance, convert hertz to kilograms as one measures the property of mass and the other the property of time.

Join Shiken For FREE

Gumbo Study Buddy

Explore More Subject Explanations

Try Shiken Premium
for Free

14-day free trial. Cancel anytime.
Get Started
Join 20,000+ learners worldwide.
The first 14 days are on us
96% of learners report x2 faster learning
Free hands-on onboarding & support
Cancel Anytime