Help Me Hill Height for 35kg Child on 5kg Sled

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Homework Help Overview

The problem involves a 35-kg child and a 5-kg sled descending a hill, reaching a speed of 30 km/h at the bottom. The hill is inclined at 25 degrees, and the question seeks to determine the height of the hill under the assumption of no friction or air resistance.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the conservation of energy, questioning the forms of energy involved at the bottom of the hill and the initial potential energy. There is an exploration of the relationship between kinetic and potential energy through relevant formulas.

Discussion Status

Some participants have confirmed their understanding of kinetic energy and potential energy, while others are working through the implications of the formulas involved. Guidance has been offered regarding the symbolic approach to solving the problem before substituting numerical values.

Contextual Notes

Participants note the importance of using appropriate units for velocity and the need for conversions, indicating a focus on precision in calculations.

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Homework Statement


A 35-kg child goes down a hill on a 5-kg sled. Starting from rest, she reaches a speed of 30 km/h at the bottom of the hill. The hill makes an angle of 25 degrees with the horizontal.

(a) Assuming there is no heat generated by friction and air resistance, how high is the hill?

I don't really know how to solve this problem, help, please?
 
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Are you familiar with conservation of energy?
What form of energy does the child have at the bottom of the hill? Where did this energy come from?
Hint: In this case, the mass of the child and sled and the angle of the hill aren't required to find the answer (as long as you work symbolically and don't try to plug any numbers in until the very end, which is generally the best approach)
 
I am familiar with COE and I think it has KE at the bottom of the hill...?
 
GalacticSnipes said:
I am familiar with COE and I think it has KE at the bottom of the hill...?

Correct. And do you know the formula for KE? What form of potential energy did the sled start with? Do you know the formula for that form of energy?
 
would the whole formula be something like this: 0.5m(v)^2 = mgh?
 
GalacticSnipes said:
would the whole formula be something like this: 0.5m(v)^2 = mgh?

Correct. Good work. Be sure to use the appropriate unit for velocity, a conversion in necessary.
 
ok, thx
 

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