5. On Bob\'s Burlap-Sack-Slide-Ride, riders start from rest at the top of the sl
ID: 1884293 • Letter: 5
Question
5. On Bob's Burlap-Sack-Slide-Ride, riders start from rest at the top of the slide as shown. They slide down a 30° incline, then a 10 meter horizontal portion. The coefficient of friction the sack and all parts of the slide is 0.12. Unfortunately, Bob placed the slide in front of a brick wall. Bob reckons that the riders will stop before hitting the wall. A). Do the riders hit the wall? (Hint: do the riders have more potential energy than is taken out by work done by friction?) B) If so, how fast are the riders traveling when they hit the brick wall? If not, where do the riders stop? between 20m 30° 10mExplanation / Answer
initial potnetial energy Ui = m*g*h
final potneital energy Ug = 0
work done by gravitational force Wg = Ui - Ug = m*g*h
work done by frictional force Wf = -uk*m*g*costheta*L - uk*m*g*x
L = h/sintheta = 20/sin30 = 40 m
x = 10 m
total work = Wg + Wf
from wrok energy relation total work = change in KE = Kf - Ki
if they stop before hitting
kf = 0
Wtotal = 0
but Wtotal = m*g*h - uk*m*g*costheta*L - uk*m*g*x = 14.6*m*g
the rider will not stop before hitting
the rider will hit the wall <<------answer
-----------------------------------
total work = Kf - Ki
14.6*m*g = (1/2)*m*(vf^2 - vi^2)
initial vi = 0
14.6*9.8 = (1/2)*vf^2
vf = 17 m/s <<<--------------ANSWER
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