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

2. Day #3
Free-Fall

9. When using metric units (like meters), use a = -9.8 m/s2
When using English units (like ft or yds), use a = ft/s2
UP +, DOWN -
a = -9.8 m/s2
v1 = 0
Do NOT memorize these. Use the basic equations of motion and simply to get these.

10. So….what does -9.8 m/s2 mean again?
It means that an object speeds up by 9.8 m/s (downward) after every second that it falls.

11. -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 + -

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

13. 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 

14. 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?)

15. 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!

16. 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