Originally Posted by HiYoSilver
I don't quite understand the physics. Please expand your explanation. This is a very very interesting concept.
If power is the same, and speed is the same, just how is muscle force lower?
Imagine lifting 200 pounds of bricks in a bucket using rope and pulleys. You could use a simple pulley setup with just one pulley at the top, and you would have to pull down with 200 pounds of force on the rope.
If you used a
block and tackle setup, where the rope makes multiple passes from the upper pulleys to the bucket, you don't have to pull as hard on the rope to move the bucket, but you have to pull more length of rope to get the same movement of bucket.
Pulling 40 feet of rope with 100 pounds of force is considerably easier than pulling 20 feet of rope with 200 pounds of force. The important thing to note is that regardless of what solution you utilize, you still end up lifting 200 pounds of bricks 20 feet.
I'm fairly confident in my explanation, but if I've got this wrong feel free to jump in and set me straight. Basically, you use less muscle power by spinning faster (pulling more rope) in a lower gear (lighter pull) but you can still move the bike at the same speed (200lbs/20ft).