Introduction to Freefall

FLHS

Ms. Li

AIM: Which one falling faster? Kiwi & Straw Mousers or Astronauts?

LO: An object in free fall accelerates due to the force of gravity

LO: Use the motion equations to solve problem involving freely falling objects

2.6 Freely Falling Bodies

2.6 Freely Falling Bodies

In the absence of air resistance, it is found that all bodies at the same location above the earth fall vertically with the same acceleration.

2.6 Freely Falling Bodies

In the absence of air resistance, it is found that all bodies at the same location above the earth fall vertically with the same acceleration.

Furthermore, if the distance of the fall is small compared to the radius of the earth, the acceleration remains essentially constant throughout the fall.

2.6 Freely Falling Bodies

In the absence of air resistance, it is found that all bodies at the same location above the earth fall vertically with the same acceleration.

Furthermore, if the distance of the fall is small compared to the radius of the earth, the acceleration remains essentially constant throughout the fall.

This idealized motion, in which air resistance is neglected and the acceleration is nearly constant, is known as free-fall.

2.6 Freely Falling Bodies

In the absence of air resistance, it is found that all bodies at the same location above the earth fall vertically with the same acceleration.

Furthermore, if the distance of the fall is small compared to the radius of the earth, the acceleration remains essentially constant throughout the fall.

This idealized motion, in which air resistance is neglected and the acceleration is nearly constant, is known as free-fall.

Since the acceleration is constant in free-fall, the equations of kinematics can be used.

Acceleration Due to GravityThe acceleration of a freely falling body is called the acceleration due to gravity, g.

The acceleration due to gravity is directed downward, toward the center of the earth.

Near the earth's surface, g = 9.81 m/s2, down.

Heavy and light objects fall at the same rate

A Falling Stone

A stone is dropped from rest from the top of a tall building, as the figure indicates.

After 3.00 s of free-fall, a. what is the velocity v of the stone?

b. what is the displacement d of the stone?

Coin TossA football game customarily begins with a coin toss to determine who kicks off. The referee tosses the coin up with an initial speed of 6.00 m/s. In the absence of air resistance, how high does the coin go above its point of release?

What is the velocity and acceleration at the maximum height?

Free Fall and the Acceleration of Gravity

• Free-falling objects do not encounter air resistance. (IAF)

• All free-falling objects (on Earth) accelerate downwards at a rate of approximately 10 m/s/s (to be exact, 9.8 m/s/s)

“G”

• the acceleration of gravity is such an important quantity that physicists have a special symbol to denote it - the symbol g

• g = 10 m/s/s, downward

Graphing Freefall

Graphing Freefall 2

Other Equations

a = accelerationd = displacement/distancet = time intervalv = velocity/speed = average velocity/average speed∆ = change

Equations

vf = g * t

Final Velocity

Distance Traveled

d = 0.5 * g * t2

Example

Given:vi = 0.0 m/s d = -8.52 ma = - 9.8 m/s2

Find: t = ??

Example 2

Given:vi = 26.2 m/s

vf = 0 m/s

a = -9.8 m/s2

Find:d = ??