05-04-2018, 11:23 PM
If the air resistance goes up with the square of the speed, the air resistance would increase by 1.9 times from 55mph to 75mph, and if rolling resistance (tyre and frictional power consumption etc) increase is linear, then the total power required at 75mph would be 2.5 times that at 55mph. However, the Wikipedia article on rolling resistance says: "Rolling resistance greatly increases with applied torque. At high torques, which apply a tangential force to the road of about half the weight of the vehicle, the rolling resistance may triple (a 200% increase). This is in part due to a slip of about 5%. The rolling resistance increase with applied torque is not linear, but increases at a faster rate as the torque becomes higher." Therefore, a power of more than 2.5 times might be required to reach 75mph?
Colin
Colin