Okay, so in practice a unicycle rider (or unic) is always accelerating, decelerating, turning, compensating for uneven ground, and what have you. But let's assume a unic moving at constant speed in a straight line over perfectly smooth flat ground for the sake of physics. The rider is positioned so her center of mass is directly over the contact point of the wheel with the ground. Gravity exerts a force straight down on her center of mass. The ground exerts a force in the direction from the contact point of the wheel up to her center of mass. Since we're starting in equilibrium, this is exactly equal and opposite to the gravitational force.
Now she unexpectedly hits a rock. The wheel suddenly slows down, but her center of mass keeps moving forward at the same speed. Now gravity is still pushing straight down, but the ground is pushing up at an angle and she begins to fall forward.
She quickly responds by pedaling harder, causing the wheel to accelerate and increasing the magnitude of the upward force vector. The vertical component of the two vectors equal each other and she does not fall down and instead rights herself. But the forward component of the ground vector has accelerated her, meaning she is now traveling faster than before.
To slow down, she basically reverses the process in a more controlled manner, leaning back as she pedals more slowly, keeping the forces and torques in balance.
That is, assuming she can apply the required force to the wheel fast enough. There are lots of reasons why she might not be able to, including her speed, reaction time, position of the pedals, and if she is in fact not traveling in a straight line but is instead playing hockey and has just fired off a slapshot on goal, meaning her body is twisted and trying to move in one direction, while her wheel is trying to move in another direction and angular momentum is trying to conserve itself.
Then she falls down. This happens to me every couple of miles or so. Usually I land on my feet while my uni clatters to the ground behind me. Very rarely I land on something other than my feet, which tends to be very painful.
That's all if the bump is unexpected. If you know it's coming it's easy to get the speeds and forces set up ahead of time. I routinely ride up over two inch curbs and down two or three steps in a row. I knew a guy who rode down over drops of two feet or more, equal to the diameter of his wheel, until he blew out the frame of his uni.
Then he built a stronger frame.
The Uno, however, works the same way as a Segway. You control it by leaning, so if you hit a bump, it should take care of all the speed changes for you. And if you're riding along and someone steps out in front of you, you'll lean hard out of the way, and it will accelerate or corner hard to prevent you from falling off, and you'll dodge the pedestrian and everyone will keep going where they were headed.
I think it is fair to ask how hard it can accelerate, but if they intend it for street riding I hope the answer is pretty hard.
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timeasmymeasure
no subject
Date: 2008-08-07 11:26 pm (UTC)Now she unexpectedly hits a rock. The wheel suddenly slows down, but her center of mass keeps moving forward at the same speed. Now gravity is still pushing straight down, but the ground is pushing up at an angle and she begins to fall forward.
She quickly responds by pedaling harder, causing the wheel to accelerate and increasing the magnitude of the upward force vector. The vertical component of the two vectors equal each other and she does not fall down and instead rights herself. But the forward component of the ground vector has accelerated her, meaning she is now traveling faster than before.
To slow down, she basically reverses the process in a more controlled manner, leaning back as she pedals more slowly, keeping the forces and torques in balance.
That is, assuming she can apply the required force to the wheel fast enough. There are lots of reasons why she might not be able to, including her speed, reaction time, position of the pedals, and if she is in fact not traveling in a straight line but is instead playing hockey and has just fired off a slapshot on goal, meaning her body is twisted and trying to move in one direction, while her wheel is trying to move in another direction and angular momentum is trying to conserve itself.
Then she falls down. This happens to me every couple of miles or so. Usually I land on my feet while my uni clatters to the ground behind me. Very rarely I land on something other than my feet, which tends to be very painful.
That's all if the bump is unexpected. If you know it's coming it's easy to get the speeds and forces set up ahead of time. I routinely ride up over two inch curbs and down two or three steps in a row. I knew a guy who rode down over drops of two feet or more, equal to the diameter of his wheel, until he blew out the frame of his uni.
Then he built a stronger frame.
The Uno, however, works the same way as a Segway. You control it by leaning, so if you hit a bump, it should take care of all the speed changes for you. And if you're riding along and someone steps out in front of you, you'll lean hard out of the way, and it will accelerate or corner hard to prevent you from falling off, and you'll dodge the pedestrian and everyone will keep going where they were headed.
I think it is fair to ask how hard it can accelerate, but if they intend it for street riding I hope the answer is pretty hard.