Freefall

Did you watch the video?http://aplusphysics.com/courses/regents/videos/FreeFall_Regents/FreeFall_Regents.html

• “Freefall”- an object acted upon only by the force of gravity

• “acceleration due to gravity” on Earth = 9.81 m/s2

• We are going to use 10 m/s2

• When drag is equal to weight, there is no net external force on the object and the vertical acceleration goes to zero.

• With no acceleration, the object falls at a constant velocity as described by Newton's first law of motion.

• The constant vertical velocity is called the terminal velocity .

In freefall you actually don’t accelerate forever…

Freefall Table-Analyzing velocity and distance of an object

“dropped” (vi = 0, a = 10 m/s2) over a period of time.t (s) vf (m/s) d (m)

0

1

2

3

4

5

6

7

8

9

10

vf = ?What equation?

0

d = ?What equation?

0

Practice:

A rock is dropped from a bridge over a river. How far did the rock fall after 4 s? What is the velocity of the rock 4 seconds after it is dropped?

Orange Review Book:

Throw up Problems:

• What goes up must come down- symmetry of motion

• time up = time down• vi = vf

• Peak of motion v = 0 m/s

Practice:• An arrow is shot vertically into the air. The arrow returns to earth 10

seconds later.– What time did it take the arrow to reach it’s highest point?– Find the arrows speed at it’s highest point.– Find the arrows acceleration at it’s highest point.– Find the speed of the arrow the instant before it lands.– What is the displacement of the arrow after it lands?