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O DA 98% Tue Jun 14 7 50 46 PM QA E Chrome File Edit View History Bookmarks People Window Help f Facebook Josh Conservation of energy/W. b www.webassign.net 13907360 /web/Student/Assignment-Responses/last?dep App Bookmarks Apple YouTube home Watch Live Sports E O tech Destiny LFG.Net l The faculty.pnc.edu/ptes DTR Destiny Tracker De Eii C. Henry Edwards, Additional Materials L Section 6.6 3. -1 points CJ10 6. 015 My Notes Ask Your Teacher It takes 160 kJ of work to accelerate a car from 22.5 m/s to 27.5 m/s. What is the car's mass? kg Additional Materials Section 6.2 4. C+D -1 points CJ10 6. 020 My Notes Ask Your Teacher A 17 kg sled is being pulled along the horizontal snow-covered ground by a horizontal force of 22 N. Starting from rest, the sled attains a speed of 1.8 m/s in 7.9 m. Find the coefficient of kinetic friction between the runners of the sled and the snow. Additional Materials Section 6.2Explanation / Answer
From the wor energy theorem
W = 1/2 mv2^2 - 1/2 mv1^2
m = W / 1/2 v2^2 - 1/2 v1^2
= 160 * 10^3 J/ / 0.5(27.5)^2 - 0.5(22.5)^2
=1280 kg
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(4)
Apply Newton's second law to the sled
F- fk = ma
F-uk N = ma
F- uk mg = ma
uk = F- ma/mg
from the kinematic equation
v^2 - u^2 = 2as
a = v^2- u^2/ 2s = 1.8^2 - 0/ 2( 7.9 m
=0.205 m/s^2
uk = 22 N - (17) ( 0.205 m/s^2)/17( 9.8)
=0.111
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