Reading Assignment: Chapter 6 of Tippens.

Today's lecture is dedicated to a review for tomorrow's mid-term exam. Most of the lectures is spent discussing Word Problems. With the two kinematical equations that will be convered on the exam:
x = x0 + vt
v = v0 + at
there are only a few types of questions possible. Three general kinds of questions come from the 1st equation (velocity problems in the abstract), and three kins of questions come from the 2nd equation (acceleration problems in the abstract). Some examples of concrete problems are presented here and answers are presented here. A mastery of these problems and Problems numbers 12-1 through 12-12 at the end of Ch. 6 in Tippens would be good material to study for the exam.
We close with two warnings.....to be careful out there!
(1) In doing problems with falling bodies in a vacuum (i.e., neglecting air resistance) it is important to remember that during the body's entire flight it is subjected to the same constant acceleration, the acceleration of gravity, whose magnitude is about 9.8 m/s^2 in the downward direction. This value is called 1 g. The sign on this acceleration depends on the coordinate system chosen. If positive it up, then the acceleration of gravity is -9.8 m/s^2. Hpwever, if positive is down, then the acceleration of gravity is +9.8 m/s^2.
(2) In doing problems for bodies thrown up into the air, remember two things. First, when the body reaches its highest point, it stops instantaneously. Thus, at its highest point velocity is momentarily zero. This does not mean that acceleration goes to zero at this point. Warning (1) above tells us that the body undergoes the same acceleration of gravity regardless of its motion. Second, the flight of the body is symmetric about its top point. That is, at any height the velocity of the ball on the way down is equal in magnitude but opposite in direction to the velocity of the ball on the way down. Thus, when it comes back to its initial location it will be traveling with the same speed as when it was released for its upward journey.

Link for the Day: Physics 1000, 1995 (See Exam 1)

Questions or comments should be addressed to Mike Ritzwoller at ritzwoller@phys-geophys.colorado.edu 

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