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How to convert km/h to rpm ?
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The formula to convert a linear velocity expressed in kilometres per hour [km/h] to an angular velocity expressed in revolutions per minute [rpm] is given by:

N(rpm)=253×π×rv(km/h)N_{(rpm)} = \frac{25}{3 \times \pi \times r} v_{(km/h)}

Where:

  • vv is the linear velocity expressed in kilometres per hour (km/h)
  • NN is the angular velocity expressed in revolution per minute (rpm)
  • rr is the radius expressed in meters (m)

Here is an online converter from km/h to rpm.

To convert speed from kilometers per hour (km/h) to revolutions per minute (rpm), you need to know the circumference of the wheel or rotating object that the speed is associated with. Here's a step-by-step guide to perform the conversion:

  1. Determine the Wheel Circumference:

    • The circumference CC of the wheel can be calculated using the formula:
      C=π×dC = \pi \times d
      where dd is the diameter of the wheel.

  2. Convert km/h to meters per minute (m/min):

    • Since 1 kilometer = 1000 meters and 1 hour = 60 minutes, the conversion from km/h to m/min is:
      Speed (m/min)=Speed (km/h)×100060\text{Speed (m/min)} = \text{Speed (km/h)} \times \frac{1000}{60}

  3. Calculate the Revolutions per Minute (rpm):

    • Once you have the speed in meters per minute and the circumference in meters, you can calculate the rpm:
      RPM=Speed (m/min)Circumference (m)\text{RPM} = \frac{\text{Speed (m/min)}}{\text{Circumference (m)}}

Example Calculation

Suppose you have a vehicle moving at 60 km/h with a wheel diameter of 0.7 meters. Let's convert this speed to rpm.

  1. Calculate the wheel circumference:

    C=π×0.7≈3.14×0.7≈2.198 metersC = \pi \times 0.7 \approx 3.14 \times 0.7 \approx 2.198 \text{ meters}

  2. Convert 60 km/h to meters per minute:

    Speed (m/min)=60×100060=1000 m/min\text{Speed (m/min)} = 60 \times \frac{1000}{60} = 1000 \text{ m/min}

  3. Calculate the RPM:

    RPM=10002.198≈455.87\text{RPM} = \frac{1000}{2.198} \approx 455.87

So, at 60 km/h, the wheels would be rotating at approximately 456 rpm.

General Formula

If you want a general formula:

  1. Convert km/h to m/min:
    Speed (m/min)=Speed (km/h)×16.6667\text{Speed (m/min)} = \text{Speed (km/h)} \times 16.6667

  2. Use the formula for RPM:

    RPM=Speed (km/h)×16.6667π×Wheel Diameter (m)\text{RPM} = \frac{\text{Speed (km/h)} \times 16.6667}{\pi \times \text{Wheel Diameter (m)}}

This formula can be used for any given speed and wheel diameter.