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# Power (Torque x Rpm) need to move 100kg car to 1.86 MPH/3 KMH in about 3 seconds? Answered

I am planning to build the electric car. But having no experience in physics.

My Electric car have following specification:
-> 4 Wheel Car
-> 100Kg car weight including Person weight
-> Wheel size can be 4-8 inch

I want to move the car on flat road (No incline) to about 3-4KMH / 1.86-2.48MPH in about 3-5 seconds. I want to know that how much power it needs to attain that speed. Also I want to know that how much power it needs to overcome rolling friction in order to move the car.

I have the dc motor of 2kg.cm or 0.2N.M torque and 7k rpm, can I use this motor to attain that speed.

Also please can someone tell me the formula according to my specification so I will alter the wheel size value to calculate the power needed to attain that speed.

Also is the torque of 2kg.cm or 0.2N.M and 7k rpm is enough to move the car or I have to setup the gearing? If have to setup the gearing then can you please tell me the ratio.

Thank  You!

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## Discussions

To clarify, you need a motor (and a power supply) to move you at 3-4 km/h for 3-5 seconds, right?

First off, the motor you have currently is too weak and too fast. You will most defiantly need a gearbox.

Second, in a perfect world, we could calculate the torque needed. Seeing as we don't live in a perfect world, where we have uneven roads, air pressure, unequal friction.

Just as rickharris said, just experiment with a scale and different motors.

Good luck!

The speed you looking for is very slow. Try pushing the car with a weight scale against it so you can measure the force involved.

Any motor will need to be geared down a LOT.

You don't mention power available so I suggest you start by trying a car windscreen wiper motor and see how you go. It will be cheap enough to experiment with.