A skateboarder with a mass of 68.6 kg and a speed of 4.92 m/s coasts across a parking lot. After coasting for 35.0 m the skateboarder has a speed of 1.12 m/s. How much work has been done against friction?
a) 338 J
b) 76.8 J
c) 7.5 J
d) 787 J
2 answers
1/2 * 68.6 * (4.92^2 - 1.12^2)
Work = Change in Ek
mvfinal squared divided by 2 - mvinitial squared divided by 2
=-787
mvfinal squared divided by 2 - mvinitial squared divided by 2
=-787