Student "edition" found at {csi dot journalspace dot com}.

Maybe I shouldn't have started this blog now, not with everything that's been going on.

In my most recent lecture for the general science requirement mechanics class, we moved on from just getting the resultant force from two or three forces acting on the same object to using the given acceleration from that equation of the system to tie it in to the initial and instantaneous velocity we’ve discussed before, as well as the time and displacement of the object in motion.

The students have to understand that several forces acting on the same system results in only one acceleration (which may be zero if the forces cancel out) which is now in the same direction as the motion, thus the displacement and the velocity.

But that for every point along the motion of the object, it will have a different (but not necessarily unique) value for velocity, time and displacement. Acceleration and initial velocity will remain the same all throughout though.

After that example, I gave them an example that was in reverse, where three out of the following quantities were given first: initial velocity, time, displacement or final velocity. Also given in the problem is the mass of the object, and the direction of motion, as well as all but one of the forces acting on the object.

What is usually asked for there is the magnitude and direction of the missing force.

This they will have to derive by first solving for the acceleration of the object using the equations we have to constant acceleration, and from there they have to get the summation of forces by using the mass. Using the direction, they can thus now get the x and y components of the final force.

They have to use the same equations to get the components of the other forces given, and they have to subtract these from the final force to get the components of the missing force. Then they have to use the right triangle equations to get the resultant magnitude and direction of the missing force.

I was planning to introduce the next lesson after this, the two-dimensional motion as seen from the side view, starting with projectile motion, but they asked for another example.

I ended up just having three problems for that meeting, four if their exercise is included.

That means we spent about twenty two and a half minutes on each problem.

Session 1519 wanted to absorb the old lesson before the new lesson was introduced. Class dismissed.