Does the current speed matter when accelerating?

[shlosmem]

Neglecting the air resistance, is it more difficult for a biker with a proper gearing in his bike, to increase his speed by 5 kph if his current speed is 20 kph rather then if his speed is 10 kph?
It seems that the answer is yes according to the energy formula but I've asked several bikers and they say they never notice it. So maybe I wrong here?

 

[PeroK]

Neglecting the air resistance, is it more difficult for a biker with a proper gearing in his bike, to increase his speed by 5 kph if his current speed is 20 kph rather then if his speed is 10 kph?
It seems that the answer is yes according to the energy formula but I've asked several bikers and they say they never notice it. So maybe I wrong here?

It certainly takes more power to maintain a constant acceleration. Eventually you notice it because the bike cannot go any faster. That's partly the increasing resisting forces, but mainly the energy/power requirements.

 

[Dale]

I've asked several bikers and they say they never notice it. So maybe I wrong here?

That is the main reason bikes have gears. Don’t shift gears and I bet they will notice.

 

[russ_watters]

Neglecting the air resistance, is it more difficult for a biker with a proper gearing in his bike, to increase his speed by 5 kph if his current speed is 20 kph rather then if his speed is 10 kph?
It seems that the answer is yes according to the energy formula but I've asked several bikers and they say they never notice it. So maybe I wrong here?

The issue is: what, exactly, are they "noticing"? Except in the beginning of a start from a complete stop, a bicyclist will tend to accelerate at constant power to avoid unnecessary fatigue. If they "notice" the "effort" (power) is the same, that's true. But maybe they aren't paying attention to/"noticing" that it takes much longer to accelerate from 20-25 than from 10-15.

 

[jack action]

It takes more fuel to go from 20 to 25 than 10 to 15, but how much fuel is left in the "tank" is not something noticeable at the moment you are accelerating.

The assumption that is missing from you hypothesis is how they accelerate. If the slower rider accelerates at, say, 2 kph/s (2.5 s to reach 15 kph) and the fast rider accelerates at 1 kph/s (5 s to reach 25 kph), then both will use the same power input (force times velocity). This means that - with appropriate gearing - the same effort (crankset torque and rpm) can propel both bikes. The only difference being that the fast rider will have to maintain it twice as long.

If the acceleration must be the same in both cases, then the fast rider will need twice the power and will obviously notice it.

 

[jbriggs444]

A cyclist adopting a reasonably fixed cadence will be in twice as high a gear at 20 mph as at 10 mph. At a consistent effort, this means half the torque delivered to wheels rotating at twice the speed.

Gaining an incremental 5 miles per hour takes twice as long because the available torque is halved.

That is before one considers the effects of wind resistance -- which draws power as the cube of speed.