I dont know why I am getting a different answer but here is the question: A toboggan is initially moving at a constant velocity along a snowy horizontal surface. Ignore friction. When a pulling force is applied parallel to the ground over a certain distance, the kinetic energy increases by 47%. By what percentage would the kinetic energy have changed if the pulling force had been at an angle of 38° above the horizontal? A few things: Ekf = Final kinetic energy Eki = Initial kinetic energy m=mass vf=final velocity vi=initial velocity Now: Case 1 (where the force applied is parallel to the ground) 2Facos0(mvf-mvi)=2(100 x 0.47) mvf-mvi=(100 x 0.47)/Fa Case 2 (where the force is at 38° to the horizontal) 2Facos38(mvf-mvi)=2(100 x y) mvf-mvi= (100 x y )/FaCos38 Now equating the two equations: 100 x 0.47 = (100 x y)/cos38 Solving for y I got y=0.37 So the increase is ~ 10%, and the answer is 16%. What did I do wrong?