Calculating Work Done by Friction in a Downhill Race: Conservation of Motion

In summary, a boy in a wheelchair with a total mass of 48.7 kg wins a race with a skateboarder by having a speed of 1.23 m/s at the crest of a slope 2.37 m high and 14.0 m long. At the bottom of the slope, his speed is 6.27 m/s. By using the equations for work and taking into account the constant frictional force of 41.8 N for air and rolling resistance, the work he did in pushing forward on his wheels during the downhill ride can be calculated. The work done by gravity can be calculated as (48.7)(9.8)(2.37) = 1149.7 J, and
  • #1
Chuck 86
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0

Homework Statement


boy in a wheelchair (total mass, 48.7 kg) wins a race with a skateboarder. He has a speed of 1.23 m/s at the crest of a slope 2.37 m high and 14.0 m long. At the bottom of the slope, his speed is 6.27 m/s. If air resistance and rolling resistance can be modeled as a constant frictional force of 41.8 N, calculate the work he did in pushing forward on his wheels during the downhill ride.


Homework Equations


Ei-Ef=Wfriction+Woutside forces

1/2mv^2, mgh

The Attempt at a Solution


cant seem to set this up right. don't know the equations for the 2 work
 
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  • #2
Can't you think of a general expression for work that you could use here?
 
  • #3
Not of the outside forces
 
  • #4
that would be cool to get some help instead of pointing out that I am not smart, that's why I am asking for help
 
  • #5
What are the outside forces?

In particular, what is the work done by gravity?
 
  • #6
MgH=(48.7)(9.8)(14)
 
  • #7
OK but H=2.37 m here, not 14m.

Now you just need to calculate the work done by friction.
 

1. What is the conservation of motion?

The conservation of motion is a fundamental principle in physics that states that the total linear momentum of a closed system remains constant over time, regardless of any external forces acting on the system.

2. Why is the conservation of motion important?

The conservation of motion is important because it allows us to predict the behavior of objects in motion and understand the fundamental laws of nature. It also has numerous practical applications, such as in engineering and technology.

3. How does the conservation of motion relate to Newton's laws of motion?

The conservation of motion is closely related to Newton's laws of motion, specifically the first and second laws. The first law states that an object will remain at rest or in motion with constant velocity unless acted upon by an external force. The second law states that the net force acting on an object is equal to its mass times its acceleration. Together, these laws explain the concept of conservation of motion.

4. Can the conservation of motion be violated?

No, the conservation of motion is a fundamental law of nature and has been extensively tested and observed to be true. While it may appear to be violated in certain situations, closer examination will reveal that external forces are at play and the total momentum of the system is still conserved.

5. What are some real-life examples of the conservation of motion?

Some real-life examples of the conservation of motion include a moving car coming to a stop when the brakes are applied, a ball bouncing off a wall, and a pendulum swinging back and forth. In all of these situations, the total momentum of the system remains constant, even though there may be external forces acting on the objects.

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