Thoughts on your approach to #341:
1. Just a refresher - F in the W = Fd is not always just the gravitational force, it refers to the net force. However, that's not important here because the gravitational force is the only force present.
2. Ok, so why is an angle going to affect this equation? Simply, because the object is on an inclined (i.e. angled) plane. Here's the science: if the force of gravity as we normally know it (mg) was dictating the direction of the object's motion, it would move down
through the incline plane, but that's obviously not what we see. We see the object "slide" down and to the side (left in this example) meaning gravity is acting in some capacity to pull the object down but not straight down in the way we'd see a falling object fall. So the portion of the gravitational force that's forcing this object to move is equal to mg
sin(theta) = the effective x-direction vector of gravity.
So now our equation looks like this
W = mgsin(theta)*d
#342:
@Czarcasm explains this very well. The answer is A. You can also look at the Work equation we concluded in #341 and realize that mass is present in the equation. So when mass changes, work must too - not the case for velocity, time, and acceleration. Another way to quickly remember this is that all of the translational/kinematics equations you are to memorize for MCAT physics do not take into account mass, but they do take into account time, velocity, distance, and acceleration. The former variable, mass, is independent of these latter variables within the concept of kinematics.