Which action would prevent a fracture in the cyclist?

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In summary, the conversation discusses how to prevent a cyclist from fracturing his arm in an accident. The options given are to decrease the velocity or the mass by a factor of 2. The correct approach is to increase the time it takes to change velocity, resulting in lower acceleration and force. This can be explained through Newton's 2nd Law, momentum, and kinetic energy. However, it is important to note that all arguments lead to the same conclusion. The conversation also touches on the impact time and kinetic energy in relation to velocity and mass. Finally, the biggest factor in the energy equation that can lead to a fracture is the kinetic energy.
  • #1
nothing123
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Let's say a cyclist hits a tree and fractures his arm. Which of the following would have likely prevented the fracture:

a) decrease in his velocity by factor of 2
b) decrease in his mass by factor of 2

What arguments can be used here to reason this (ex. momentum, energy, force)? Immediately when I rephrased the question in my head to what change would have reduced the damage the most and thought of force. However, I guess you could also use the kinetic energy argument. I'm a little confused as to what the correct way to approach this is. At any rate, shouldn't all arguments lead to the same conclusion?

Thanks.
 
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  • #2
From Newton's 2nd Law, F=ma. If you can increase the time it takes to change velocity, then the impact time increases resulting in lower acceleration, thus lower the force.
From momentum, p=mv. If you decrease velocity by a factor of 2 in one case, and decrease mass by a factor of 2 in another case, I believe you will get the same momentum in both cases, but a difference in impact time and kinetic energy.
For kinetic energy, an average person weighs about 70kg, and a normal bike speed is ~15mph(which converts to ~6.7m/s). The kinetic energy when the velocity is halved is much less than when the mass is halved. I hope this help
 
  • #3
But can we assume we're actually increasing/decreasing impact time?
 
  • #4
[tex]velocity=\frac{distance}{time}[/tex]
Holding distance fixed, if we increase the velocity, then the impact time decreases. If we decrease the velocity, the impact time increases.
 
  • #5
E = 1/2mv^2

The energy dissipated by the guys arm broke it. Which part of the energy equation has the biggest impact on the value of E?
 

What is the most common cause of fractures in cyclists?

The most common cause of fractures in cyclists is falling off the bike and landing on a hard surface, such as pavement or rocks.

How can a cyclist minimize their risk of fractures?

A cyclist can minimize their risk of fractures by wearing proper protective gear, such as a helmet, knee and elbow pads, and padded gloves. They should also practice proper riding techniques and avoid hazardous road conditions.

Which part of the body is most susceptible to fractures in cycling accidents?

The most susceptible part of the body to fractures in cycling accidents is the upper extremities, including the wrists, arms, and shoulders. This is because cyclists often use their arms to break their fall.

Can a cyclist's diet and exercise routine impact their risk of fractures?

Yes, a cyclist's diet and exercise routine can impact their risk of fractures. Consuming enough calcium and vitamin D can help strengthen bones, and regular weight-bearing exercise can improve bone density and decrease the risk of fractures.

What should a cyclist do if they experience a fracture?

If a cyclist experiences a fracture, they should seek medical attention immediately. They should also immobilize the affected area and avoid putting weight on it until they can see a doctor.

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