Do you mean I should be applying that law to everything, or that my (a) answer is incorrect?
If you meant I should be applying that law, I can see how (e) would change to "from the floor." Would that make (c) from the floor as well? I don't think (b) or (d) would change (am I right?).
Homework Statement
For a technology project, a student has built a vehicle, of total mass 5.70 kg, that moves itself. As shown in the figure below, it runs on two light caterpillar tracks that pass around four light wheels. A reel is attached to one of the axles and a cord originally wound on...