A driver notices that her 1080-kg car, when in neutral, slows down from 95 km/hr to 65 km/hr in about 7.0s on a flat horizontal road. Approximately what power (watts and hp) is needed to keep the car traveling at a constant 80 km/h?
Here's what I did, I calculated the energy I would need to oppose the 95-65 change and then I added the energy needed to move at 80 km/hr then I divided by 7 . I think I have a misconception + a mistake somewhere because the book's answer is different. Can someone tell me where I went wrong ?
P.s, I know I can calculate the acceleration and then use F=ma AND F=PV but I don't understand why the work isn't energy needed to oppose 95-65 + KE for V=80. If you know, please answer I have been trying to understand this for 6 hours.