Physics - Vertical Motion

OPENING QUESTION: Please reflect on yesterday's formative quiz. What part of falling object problems are working well for you? What parts are still giving you indigestion?

ARNING OBJECTIVES:

  • I will continue to evaluate my ability to solve falling object problems during today's class

CALENDAR:

Vertical motion test on Thursday (NOT to include projectile motion)

WORDS O' THE DAY:

  • gravity! gravity! gravity!

FORMULAE OBJECTUS:

    • a = (vf - vi)/(tf - ti) (definition of acceleration)

    • g = 9.81 m/s2 (acceleration an object experience on Earth) ONLY present in vertical motion (Y axis) problems

      1) vfy = viy +agt

      2) yf = yi + viyt + 1/2agt2

      3) vfy2 - viy2 = 2ag∆y

WORK O' THE DAY:

Let's get the book problems (#40, 42 and 43) knocked out in the next 30 minutes or so

Let's go back to this MOST informative (AND COMPLEX) graphic of a falling object problem:

 

There are a couple of things to keep in mind when we evaluate motion in 1 dim (vertically):

  • gravity is ALWAYS present and is ALWAYS pulling an object towards the earth @ 9.81 m/s/s. What evidence is present on the graphic that reminds us of that?

  • when an object is dropped, thrown, kicked, shot or otherwise launched upwards in vertical motion, we ALWAYS evaluate the motion as directly upwards and/or directly downwards. There is no horizontal (x) motion at all. (However, there will be when we get to projectile motion next). If we look at the graphic, that doesn't appear to be the case. Why has the author shown motion that seems to be <slightly> in error?

Here's a pretty complex graphic. Look at JUST parts A and B.

What can you determine from the values shown there?

Let's take a look at a couple of practice problems in our book: #40, 42 and 43.