Unit 2 Class Notes Accelerated Physics The Kinematics Equations (1D Equations of Motion)

Day 8 Review for test

Step #1 Write Down What You Have (Look for “Key” Words)

“Coming to a stop” “Starting from rest” “Coasting” “Maximum Height” “Dropped” v 2 = 0 v 1 = 0 v 1 = v 2 = constant v 2 = 0 a = -9.8 m/s 2

“Slowing Down” “Braking” “Speeding up” “Accelerating from rest” a = - __ a = + __

Step #3 Solve the Equation Step #4 Make sure your answer makes sense

Some Helpful Tips From the Master

Helpful Tip #1 Choose your “Key Points” in every problem…and do so wisely.

“Free-fall” “Throw up” v 1 = 0 v 2 = 0 (at top) Vertical Problems v “Throw- downs”

“Throw up / Come Down” (throw and catch at same height) v 2 = 0 (at top) Vertical Problems  t 12 =  t 23 v 1 =  -v 3

“Throw up / Come Down” (throw and catch at different heights) Use and solve quadratically for “t”  x 13 =   x 13 = 

Helpful Tip #2 Assign positive and negative to different directions.

Helpful Tip #3 When solving a quadratic equation, do so with minimal effort.

Solving a quadratic equation Choice A Choice B Factoring Choice C 2 nd Trace  Zero (on graphing calculator) Unlikely on a physics problem 

Helpful Tip #4 Get out of the habit of trying to use “Chris Farley” when “Leonardo” is necessary.

d = rt (Can be used only at constant speed) Can be used at constant speeds (a=0) or when accelerating. Awesome Dude!

Helpful Tip #5 When dealing with a chase problem, use “New-Look” Leo (built for the chase)

Chase Problems Since the two objects (A and B) end up at the same position by the end of the chase, use …

But what if… The objects start at different places? It’s already accounted for here and here

But what if… The objects start at different TIMES? You’ll need to use an extra equation relating the two times. Plug this new equation into the long equation above. Example: t A = t B + 1

Helpful Tip #6 It is always important to remember that when something is thrown up or down (or simply falls), the acceleration at ALL times is constant.

The acceleration of the ball at EVERY point on this red path (When it’s rising up, when it’s stopped, when it’s falling down) is always -9.8 m/s

An object thrown up has a constant acceleration at ALL times…. ….the acceleration due to gravity Objects rise and fall in the same amount of time (assuming no parachute ) t x t v Constant slope = constant accel.

Your training is complete. Now go, have some hot tea, and rest for the upcoming Unit 2 Test

TONIGHTS HW Complete Review Worksheet