Parents: Conferences will be from 12:20 to 7PM next Thursday, the 28th. Pick up report cards, meet teachers, and get access codes for online grades if you haven't yet.
Freshmen: Tonight read p.113-117. Problems on p.117# 1-6, and p.880, #39-43. Due tomorrow.
Today in class we finished learning about gravity and how to use the Fg = Gm1m2/r^2 equation. We also simplified things a bit and just looked at what happens when the mass of an object is doubled, halved, etc. and what happens when the distance between objects is doubled, halved, etc.
We also reviewed Newton's 1st and 2nd laws, then moved on to Newton's 3rd: Action - Reaction Force pairs. We worked some examples; some involved amusing stuff. Important to know that to find a reaction force, you just switch the objects of the action force in a sentence.
Ex: Action force = Joe's foot pushing on a ball as he kicks it.
Reaction force = The ball pushing on Joe's foot as he kicks it. (equal in size of the force, just opposite in direction). The last thing I left classes with to think about is this:
If action and reaction forces are equal in size and opposite in direction, why don't they just cancel everything out, leaving us with no net forces? The answer? They act on different things. Refer to the examples above; action force was acting on a ball, and the reaction force acts on a foot. Both items accelerate as a result.
Tomorrow we'll have some brief notes on momentum, go over the homework, and do some fun Newton's 3rd / Momentum demonstrations. Not a day you'll want to miss!
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