Here's a short YouTube video that shows we should be very wary about what we take away from any given lecture.
That is, more than likely we simply take away our prior misconceptions plus a stronger belief that we know the lecture material.
I believe a similar conclusion is true about simply reading the posted solutions to problem sets, without trying to work through the problems. That is, we all too easily can read the solutions and think, "Yes, those answers makes sense. I could have solved those."
Here's another video about trying to teach you to feel Newton's third law "in your spleen".
In the latter video I think the common misconception that people are using is likely based on another belief, specifically, if we stand on the moon then gravity feels less strong than on earth (the number one-sixth may come to mind). We've all seen enough videos of astronauts gently bouncing around on the moon that we feel this "one-sixth" belief in our spleen.
The second video points out that the typical person's generalization of the one-sixth belief to the mutual gravitational attraction of the earth and the moon is wrong. The generalization misses the fact that the one-sixth belief is based on a situation which uses the same test mass on both the earth and the moon (namely, you), rather than different test masses (i.e., the earth in one case and the moon in the other).
There are several possible conclusions to this (select all that apply):
In the same order as above: