/“Then you are left with mass x acceleration, and frictional effects. Wind and air drag is the predominant loss and speed related - hence the wonderment about not much difference. Rolling resistance is not that big a deal, comparatively; though you can certainly quibble over rough roads and ire heating etc.”/
The relative work done against rolling resistance and drag forces varies with vehicle weight and CdA. A heavy car with low CdA such as the Tesla S will have less increase in energy consumption with vehicle speed due to a larger ratio of rolling resistance force to drag force compared to a light, blocky vehicle with relatively large CdA. The two forces are equal at around 40 – 50 mph for typical sedan type vehicles with Cd = 0.32. Rolling resistance force is larger below, and drag force is larger above. Rolling resistance force is a fairly constant ~ 30 lb, and drag force ~60 lb for my car at 60 mph, so if rolling resistance force was neglected at this speed, you would be neglecting about 1/3 of the force on the vehicle. /“Acceleration is the area under the velocity curve.”/ The opposite. Acceleration is the change in velocity with time, so the derivative of velocity with respect to time. Integrating acceleration over time gives velocity. /“Everything you put into acceleration you get back in Momentum. Everything you put into a hill, you get back as potential energy.”/ Yes, if you drive on a frictionless surface in a vacuum in a vehicle with no losses. In the real world you do work against rolling resistance and drag forces during acceleration, as well as lose energy to motor/controller inefficiencies and drive train friction, so only a portion of the work done is converted to vehicle kinetic energy. You also lose energy to those when decelerating, and when going up a hill and when going down. I’ve found the opposite of these reported results. I did a 64 mile round trip mainly on interstate in normal conditions at 60-65 mph, and a trip during road construction where we crept along at 10-20 mph with constant stop/start for around 15 miles of the trip each way. Energy consumption was significantly smaller during the trip with construction. I was accelerating very slowly to very low speeds, coasting a bit, then lightly braking to stop, so not much energy was used during each acceleration. Energy consumption would be significantly higher if you are repeatedly accelerating quickly to higher speeds then quickly slowed with little or no coasting in between. I also have regen so regained some energy during each deceleration, but very little since I left clearance to the car in front of me so that after each slow acceleration I could coast until my car slowed to 5mph or less before braking (with regen). -- View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/Range-vs-Speed-tp4672366p4672379.html Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com. _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
