A person riding a bicycle along a level road does not come to rest as soon as he stops pedalling.This is due to Newton's which law?
When one stops pedalling we can say that application of force has been stopped.Newton's first law is applicable here. Newton's first law can be stated as "If a body is at rest, it will continue to be at rest and if a body is in motion with a constant velocity, it will continue to do so, if no net force acts on the body."From this law we can say that the cycle will continue in a state of constant velocity motion on a level road with little rolling resistance. If we take rolling friction into consideration, we will see that there is a net opposing force (in the absence of pedalling). Here we invoke Newton's second law. It states "The net force acting on a body is equal to rate of change of momentum of the body."If we take the direction of motion as positive, then we end up with net negative force. This produces a negative rate of change of momentum. That is, there will be negative acceleration or deceleration (or retardation). Thus starting with a certain initial velocity, the cycle will come to rest in a while following the equation of motion:v=u+atWith a being negative.
Motorcycle is a deal breaker for me. Is that wrong?
I just lost a friend on a bike, he left two kids and a wife to go it alone. the kids are 6mo and 3 years old. I tried to talk him out of the bike but he just laugh at me. A woman hit him in a parking lot at low speed. Still killed him. There are no fender benders on bikes. I have two friends who both lost a leg. and a gale in my office has a husband in a chair, hit on his bike. Tell him that. when the kid is groan he can get the bike. Don't leave him, help him understand he is needed in one peace. I sold three bikes when I got married . PS Your not old, your smart and responsible thinking of others instead of your self. I think you rock. :) jp
Can two people successfully ride a tandem bicycle, if only one of them knows how to ride a bike?
Yes. Me and my partner have a tandem and she had barely ridden a bike solo before, and still wobbles with little confidence. On the back of our tandem she can sit pedalling away, no handed. If we ride vice versa, and I'll be making weight corrections from the back, while she makes NO corrections at the front - and we crash. Every time.You do need a bit of confidence in each other though, and it's definitely a bit of a learning curve in there. For example, it's easily possible to ride a tandem from the back seat, with no-one on the front - in other words, the stoker can steer by leaning! Up front it's more upper body work than on a solo, and you have to think ahead considerably You can't change direction with a flick of the hips like on a racer, and stopping takes a lot longer. Don't ride in traffic on your first go.Communication is everything, as the stoker can't see what's coming and feels bumps in road much more. I call out 'bump' out of habit now - sometimes even when I'm in the car....As for dates, well, a friends son borrows our tandem to take all his dates out on for romantic picnics, so it works for him...
When riding a bike up a slope, at some point it takes less energy to get off and walk the bike. How do you calculate the angle when walking is better?
There are many answers saying bikes are always more efficient given the right gear. This is not entirely true. The transition point will depend on your power to weight, and your bike weight fraction.At higher speed, walking power is dominated by inertial losses. Optimal walking speed for normal people is about 1.6 m/s. Cycling is good at high speed because it allows the person to go faster without moving his legs excessively fast. Below walking speed though, there are not many advantages. The criterion we will use is where climbing speed at threshold power falls below walking speed.Transition Grade = (Power:Weight)/(Bike weight fraction)/(g)/(walking speed)Here are some data points:The best professional cyclists can output a sustained (for one hour) power of 6W/kg. An average commuting cyclist will be closer to 2W/kg.A light (UCI limit) road bike will weight about 6.8 kg. If you are a heavy rider of 100 kg, then this is about 7% of your weight. A normal commuting bike might weigh about 12 kg, and an average cyclist might weigh 80 kg, giving a fraction of 15% body weight. A heavy touring bike with some cargo might weigh 30 kg, and a light cyclist (such as Contador) might weigh 60 kg, for 50% rider weight.a light, weak cyclist riding a heavy loaded bike as given above will reach walking speed at 8.5%, above which he will ascend the hill about 50% faster without a bike.A heavy, very strong cyclist riding a very light bike will reach walking speed at about 36% grade. Above this he will ascend the hill about 7% faster without a bike.A normal commuter in this example will reach walking speed at about 11% slope.Experientially, these numbers seem about right.This is an upper bound and in both cases it’s likely other factors would make walking preferable earlier (gearing, pedaling inertia, handling, CG, etc.)
What does it mean to swim in someone's wave/draft (mentioned in the olympics)?
Okay, first off I would like to say to 'Kristy' you are wrong because drafting is legal in competitive cycling and in most cycling except triathlons with people who are not so familiar with cycling. Now to the point, I think the easiest way to explain is Im sure you've seen a boat or have been on one... Well if you see the boats wake behind it it makes a wave type thing that goes out into a V just like a regular 'V'. Thats what swimmers make while swimming, it's not as large tho as you probally notice. If a swimmer is swimming close to a lane line the V carries out as you probally know and can go into the next persons lane. This causes the water to 'Break' and it is easier to swim through that water and it takes less energy, just like if you see runners running behind each other. This is a very important thing for distant swimming and even shorter races such as the 100 as Jason Leazak swam. I hope you get the point and I have a lot of experience with this, I have been competitivly swimming for 8 years. One last thing in open water swimming people swim right behind each other and that's even more of a draft instead of swimming very close to a lane line. Hope this answered your question... Kevin Surrey, United Kingdom