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

RE-Introduction to the 1D equations of motion AND Free-fall Day 2 RE-Introduction to the 1D equations of motion AND Free-fall

Derivations of the equations (a.k.a. where the turtles come from)

…. area under curve = Leonardo

Raphael Leonardo

Do NOT memorize these. DERIVE THEM!!!! When using metric units (like meters), use a = -9.8 m/s2 When using English units (like ft or yds), use a = -32.2 ft/s2 UP +, DOWN - a = -9.8 m/s2 v1 = 0 Do NOT memorize these. DERIVE THEM!!!!

-9.8 m/s2 0 m/s -9.8 m/s -19.6 m/s -29.4 m/s -39.2 m/s -49 m/s + -

v1 = 0 a = -9.8 m/s2 Dx = -20 m Why negative? Because the diver is falling DOWNWARD

2. v1 = 0 a = -9.8 m/s2 Dx = -200 m By the way, the parachute opening (or not) wouldn’t matter in the problem. WHY? Because we are assuming that there is NO AIR, and hence NO AIR RESISTANCE to open the chute 

3. How far will the diver fall in the first 2 seconds? v1 = 0 a = -9.8 m/s2 Dt = 2 sec How far will the diver fall in the first 3 seconds? v1 = 0 a = -9.8 m/s2 Dt = 3 sec How far will the diver fall during the 3rd full second (from 2 to 3 seconds?)

The mass of the object doesn’t matter! 4. Air Resistance!!! Some objects are narrower (like pencils), and therefore the air resists their falling less. Some things are wider (like frisbees) and the air provides more resistance and slows down their fall. IMPORTANT FACT: The mass of the object doesn’t matter!

5. Sometimes the variable “y” is used instead of “x” to simply show that the object is moving vertically y v t t Notice that the object speeds up Notice that the acceleration is CONSTANT and NEGATIVE the ENTIRE way

Therefore, if amoon = 1/6 aearth 6. v1 = 0 a = a Dx = h Notice that . Therefore, if amoon = 1/6 aearth

1 2 3 1-2 2-3 1-3

TONIGHTS HW Complete pp. 62-63, #’s 78, 82, 85-87, 89-91, 95, 103