To give a 16 kg child a ride, two teenagers pull on a 3.4 kg sled with ropes, as indicated in Figure 5-26. Both teenagers pull with a force of F = 53 N at an angle of 35° relative to the forward direction, which is the direction of motion. In addition, the snow exerts a retarding force on the sled that points opposite to the direction of motion, and has a magnitude of 57 N. Find the acceleration of the sled and child. picture: http://i232.photobucket.com/albums/ee319/reddevilzofah/05-23alt.gif Okay, I've tried to solve this problem and I added all the Fx. So I did 16+3.4a=-53cos35+57 Solved for a, but the answer was wrong. Can someone tell me what I did wrong and how to fix it? Thanks!