Bobsled physics homework

In summary, a bobsled run has negligible friction between points A and D, and a coefficient of kinetic friction of µk = 0.4 between points D and E. The bobsled has a mass of 210 kg and starts from rest at point A. To find the distance x beyond point D at which the bobsled will come to a halt, we can use the conservation of energy. The total energy remains constant throughout the run, so the energy at the top of each hill is equal to the energy at the bottom. The 50m and 30m heights of the two hills do not affect the speed at point D.
  • #1
mikefitz
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http://img76.imageshack.us/img76/6271/pichp1.gif [Broken]

A bobsled run leads down a hill as sketched in the figure above. Between points A and D, friction is negligible. Between points D and E at the end of the run, the coefficient of kinetic friction is µk = 0.4. The mass of the bobsled with drivers is 210 kg and it starts from rest at point A.

Find the distance x beyond point D at which the bobsled will come to a halt.


I'm thinking the best way to approach this problem is by calculating the final speed of the bobsled (bottom of the 2nd hill) and using the mass and µk to come up with the distance.

I'm having trouble visualizing how to come up with the final speed, however. The second hill is 30m high, but the initial speed down the hill will not be 0 due to the speed the bobsled gains from the first 50m hill. Where should I begin? Thanks
 
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  • #2
Hint: Since there's no friction between A and D, what is conserved?
 
  • #3
So, since the external forces are 0 then total energy does not change from one place to the next.

energy at top = energy at bottom

But how do the 50m and 30m heights effect the speed of the sled? or do they? thanks again
 
  • #4
mikefitz said:
So, since the external forces are 0 then total energy does not change from one place to the next.

energy at top = energy at bottom
Since dissipative forces are zero, the total energy is conserved.

But how do the 50m and 30m heights effect the speed of the sled? or do they?
They certainly affect the speed of the sled as it goes over those hills, but no energy is lost. Those hills don't affect the speed at D.
 

1. What is the purpose of studying bobsled physics?

The purpose of studying bobsled physics is to understand the principles of motion, forces, and energy that affect the performance of a bobsled. This knowledge can then be applied to improve the design and performance of bobsleds, as well as help athletes optimize their techniques.

2. How does the shape of a bobsled affect its performance?

The shape of a bobsled plays a crucial role in its performance. A streamlined shape with minimal air resistance helps the bobsled reach higher speeds, while a curved shape helps with steering and control. The shape also affects the distribution of weight and the center of mass, which can impact the stability and maneuverability of the bobsled.

3. What forces act on a bobsled during a run?

Several forces act on a bobsled during a run, including gravity, air resistance, and friction. Gravity pulls the bobsled down the track, while air resistance creates drag that can slow it down. Friction between the bobsled and the track provides the necessary grip to propel the bobsled forward and control its movement.

4. How does the weight of the bobsled affect its speed?

The weight of the bobsled plays a significant role in its speed. A heavier bobsled will have more gravitational force pulling it down the track, resulting in a faster speed. However, a heavier bobsled also means more mass to accelerate, so it may take longer to reach top speeds compared to a lighter bobsled.

5. What are the key factors that determine the success of a bobsled run?

The success of a bobsled run depends on various factors, including the design and shape of the bobsled, the speed and direction of the push start, the skill and technique of the athletes, and the track conditions. Additionally, weather conditions, such as temperature and wind, can also impact the performance of a bobsled run.

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