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Find exit speed at the bottom of the ramp using kinematics only 
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#1
Jan2811, 08:09 PM

P: 4

1. The problem statement, all variables and given/known data
A professional skier's initial acceleration on fresh snow is 90% of the acceleration expected on a frictionless, inclined plane, the loss being due to friction. Due to air resistance, his acceleration slowly decreases as he picks up speed. The speed record on a mountain in Oregon is 180 kilometers per hour at the bottom of a 29.0deg slope that drops 197 m. What exit speed could a skier reach in the absence of air resistance (in km/hr)? What percentage of this ideal speed is lost to air resistance? 2. Relevant equations We are only on kinematics.... (v_final)^2 = (v_initial)^2 + 2*(a_parallel)*(x_final  x_initial) , where a_parallel = g*sin(29) 3. The attempt at a solution I used trig to solve for the length of the ramp: l*sin29 = 197 l = 406.35 m Then I plugged this into the above kinematics equation and solved for v_final: (v_final)^2 = 0 + 2*g*sin(29)*(406.35  0) v_final = 62.14 m/s I converted this to km/hr: 62.14 m/1s * 1km/1000m * 3600s/1hr = 223.7 km/hr, but this isn't the correct answer. I'm not sure where I went wrong. 


#2
Jan2911, 12:58 AM

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#3
Jan2911, 01:47 PM

P: 4

Ahh yes that is what I forgot. Thanks Sammy!



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