更新1:
4. A 100 kg box is set into motion down a rough incline from rest. A constant horizontal force F = 20 N. If the box slides down a distance of 5 m, how much work done by the applied force F?
更新2:
a. 50 J b. 50 J c. 87 J d. 87 J I'm not sure if it's M*g*sin(theta) or M*g*Cos(theta) to find the answer
更新3:
theta = 30 degree