A 56.9 kg sledder descends an 8.21-meter high hill, encountering a friction force of 11.7 N, Fill in the blanks and determine the speed of the sledder after traveling the 31.7 meters to the bottom of the hill.

Top of the hill: KE=0J PE=_ W=_
Work=_
PE=0J KE=_ At the bottom of the hill
height=8.21M

1 answer

At the top of hill:
PE = M*g*h = 56.9 * 9.8 * 8.21 = 4578 J.

At bottom of hill:
KE = PE - Fk*d.
0.5M*V^2 = 4578 - 11.7*31.7
0.5*56.9*V^2 = 4207,
V^2 = 148, V = 12.2 m/s.