I’m not talking about long uphill and downhill, but more like little “bumps” that you find on any street. like getting on the sidewalk and then getting off to the road again would need me to pedal more vs when I just ride along a flat road on my bicycle. Why. If I come back to the same level of height eventually, the downhill should accelerate my bike as much as the uphill decelerate it, right?
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>the downhill should accelerate my bike as much as the uphill decelerate it, right?
It does.
Part of the acceleration is vertically downwards, and when you hit the ground you get accelerated upwards (aka. “stop going downwards), cancelling out that portion of the acceleration and converting the energy to heat.
If you had an arbitrarily big wheel, an infinitesimally small portion of the energy would be lost this way.
Bumps don’t make the wheel any harder to turn, they make the momentum gained by one turn of the wheel (so to speak) dissipate faster, so you need to put in more wheel turns to get the same distance as if it were flat
One of the things that slows you down is called rolling resistance. This happens because your tires are bending and flattening at the point where they tough the ground. This constant cyclic bending takes energy. A more highly inflated tire will bend less and lose less energy. This is why trains are so efficient, their wheels barely bend at all as they roll. When you hit bumps, they bend your tire extra and that is an amount of energy you can’t get back. I don’t know how significant the effect is for bumps.
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