How Much Mechanical Energy Does the Skier Lose?

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Homework Help Overview

The discussion revolves around a physics problem involving a skier descending a slope, focusing on the mechanical energy lost due to friction. The problem includes parameters such as the skier's mass, the slope's length, angle, and the coefficient of friction.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants discuss the calculation of potential energy and the need to determine the vertical height from the slope's angle. There are questions about the relationship between potential energy and kinetic energy, as well as the impact of friction on energy loss.

Discussion Status

Some participants have provided insights into the calculations needed for potential energy and frictional losses. There is an acknowledgment of confusion regarding the relationship between different parts of the problem, and participants are exploring how to connect the calculations for energy loss and velocity.

Contextual Notes

There is a noted misunderstanding regarding the height of the slope, as participants clarify that the slope length is not the same as the vertical height. Additionally, the importance of unit consistency in calculations is emphasized.

bkl4life
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Homework Statement


A 60 kg skier slides from rest down a 30 m slope that makes an angle of 26 degrees with the horizontal. Assume the coefficient of friction of the slope is .2.

How much mechanical energy does the skier lose while skiing down the hill?
What is the velocity of the skier lose while skiing down the hill?




Homework Equations



w=mgh



The Attempt at a Solution


m=(60)(9.8)(30)=17640 J

I'm not sure what to do after this.
 
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H isn't 30m, the slope is 30m long (ie along the hypotonuse) you have to work out from the 26deg how high the slope is.
 
Okay, so I do

(60)(9.8)(cos26)

Is it possible to take that answer and set it up to find the velocity? Do I need part A to find part B. I'm just really confused.
 
What units does 'mgh' have, what units does your equation have?
Always put in the units - it let's you spot mistakes.
The vertical height is 30 sin(26) m

You know how muhc potential energy the skier loses, and this equals the kinetic energy they gain less the frictional losses.
The energy lost to friction is force*distance, so the length of the slope * the frictional force along the slope
 
Thanks! This makes sense. I always mess up my units!
 

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