A quick guesstimate: Calculate the work as the sum of the Kinetic Energy at 20 KM/hr + estimated drag and parasitic losses.
Take it a bit further an estimate the efficiency of your prime mover, find the heat of combustion of your fuel type, and estimate the fuel volume required.
Dear Guest, At constant power will the acceleration increase, decrease, or stay the same as the vehicle speed increases? Why?
Accelerating to 20 KM/hr and then applying the brakes to bring the vehicle to a stop - can you describe the energy conversions?
Gavilan
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"The greater danger for most of us lies not in setting our aim too high and falling short; but in setting our aim too low, and achieving our mark." -- Michelangelo
On a level road, you could hand push a 250 kg car to 20 km/h in 20 seconds.
If this sounded like a homework assignment, I wouldn't simply give you the answer... but you haven't given as much info as a homework question would have.
So... 20 km/h = 5.5 m/s
Accelerating to 5.5 m/s in 20 seconds = .275 m/s/s
F=MA so 250kg * .275 m/s/s = 69 newtons (Which is about the force you feel on your hand when you hold up 7 kg against gravity)
The power changes with speed, but if you assumed an average speed of 2.75 m/s, then the power required would be 69 newtons x 2.75 m/s = 190 watts = about one strong person power. A typical weed whacker motor would work.
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There is more to life than just eating mice.
......20km/h in 20 secs is quiet draging performance with 250 kg weight , even 150cc 13BHP engine would do better , are you trying to build a so called car with weight 250 kgs and looking for engine to push that weight , first you have to look for dry weight than total weight of persons seating or net load that can be fitted on the vehicle than look out for the engine that can perform optimumly because 20 km/hr in 20 sec is not acceptable feature , are you designing with human power.......please clear your query with detailing about application ....
Power Of A Car
Re: power of a car
