Chandne

I have several bikes. The heavier ones take more effort to keep up to speed. Heavier bikes simply require more effort to keep at 28+ for me. Not sure what Newton's Law of Motion you are referring to where it takes less effort to pedal a heavier bike. Th heavier bike will pick up speed faster (with equal tires etc.) organically on steeper downhills but maintaining speed of flats is different.

If that (your Newton's Law- prob not #2 or #3 though) were the case, I'd be flying at 30 MPG on my 30 lb mountain bike with slicks...something that I could simply never ever do on a flat but I can with my 16 lb BMC, for example. That even goes for downhill portions when you have to pedal for 30-40 flatter yards. I have almost all my PRs on the two bikes and on those 50+ MPH ones, my second lightest bike with deeper wheels. If you have to pedal hard to maintain speed, it is simply less effort to keep a light bike up to speed. I have a 28 lbs heavy gravel bike with 30s as well and while I can get that up to speed on flats eventually, it takes far more effort to keep it above 24-25.