- #1
zapnthund50
- 31
- 6
Hi guys,
Yesterday I sat down, and just for fun, decided to calculate the coefficient of kinetic friction for the all electric Ford Focus. I keep getting the wrong answer, and it is driving me crazy. Here are the facts.
Battery: 23 kWh.
Curb weight: 1,651 kg.
Maximum travel distance before a recharge: 122 km
Very simply, we take 23 kWh*3600s = 82,800,000 J.
Then, the energy traveled per km is 82,800,000/122km = 679,000 J/km.
Then, force of friction for the entire car is Ff=uk*weight = 1651uk.
Then, we just say W= 679,000 = Fd = 1651uk*1000 meters,
and thus uk=0.411
But we have it from very reliable sources that the coefficient of kinetic friction for rubber on asphalt is around 0.7, so we are very low. Also, if we take into consideration wind resistance, rolling resistance, and battery discharge to 85% (I'm guessing here) instead of 100%, all these act to lower the coefficient, not raise it.
You can see my dilemma.
Thanks!
Yesterday I sat down, and just for fun, decided to calculate the coefficient of kinetic friction for the all electric Ford Focus. I keep getting the wrong answer, and it is driving me crazy. Here are the facts.
Battery: 23 kWh.
Curb weight: 1,651 kg.
Maximum travel distance before a recharge: 122 km
Very simply, we take 23 kWh*3600s = 82,800,000 J.
Then, the energy traveled per km is 82,800,000/122km = 679,000 J/km.
Then, force of friction for the entire car is Ff=uk*weight = 1651uk.
Then, we just say W= 679,000 = Fd = 1651uk*1000 meters,
and thus uk=0.411
But we have it from very reliable sources that the coefficient of kinetic friction for rubber on asphalt is around 0.7, so we are very low. Also, if we take into consideration wind resistance, rolling resistance, and battery discharge to 85% (I'm guessing here) instead of 100%, all these act to lower the coefficient, not raise it.
You can see my dilemma.
Thanks!