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### Free Fall

### http://www.youtube.com/watch?v=PE81zGhnb0w we use the formula, where a=ghttp://www.youtube.com/watch?v=3BETTsLOgQI

By: Jasmine Ahmed, Shelley Bi, Christina Bai

What is Free Fall?

- Free fall is the motion of an object falling with a constant acceleration
- In this case, the constant acceleration would be
a = g = 9.81 m/s2, but since objects free fall towards the Earth's surface ---> a = - g = - 9.81 m/s2

- When there is no air resistance, all objects fall with the same acceleration regardless of their masses

For Example . . .

If an astronaut dropped a hammer and a feather in space, the hammer and the feather would fall towards the surface with the same acceleration, therefore they would land on the surface at the exact same time.

In free fall, the acceleration, 9.81 m/s2, remains constant. This occurs, because of the gravity near the Earth's surface.

V = at

To find the distance traveled by an object during free fall, we use the formula, where a=g

d= vit + 1/2 at2

When an object starts at rest, the formula is reduced to

d= 1/2 at2,

because the velocity is 0 m/s.

Problem 1 we use the formula, where a=g

A ball dropped from rest falls freely until it hits the ground with a speed of 20 meters per second. The time during which the ball is in free fall is approximately(1) 1 s (2) 2 s

(3) 0.5 s

(4) 10 s

Solution to Problem 1 we use the formula, where a=g

V = at

t = V

a

t = 20 m/s

-9.81 m/s^2

(2) t = 2 seconds

Problem 2 we use the formula, where a=g

An object is allowed to fall freely near the surface of a planet. The object has an acceleration due to gravity of 24 m/s2 How far will the object fall during the first second? (1) 24 meters (3) 9.8 meters (2) 12 meters (4) 4.9 meters

Solution to Problem 2 we use the formula, where a=g

d= 1/2 at2d= 1/2 (24 m/s2)(1s) (2) d= 12 m

Problem 3 we use the formula, where a=g

3. Starting from rest, object A falls freely for 2.0 seconds, and object B falls freely for 4.0 seconds. Compared with object A, object B falls

(1) one-half as far (3) three times as far

(2) twice as far (4) four times as far

Solution to Problem 3 we use the formula, where a=g

d= 1/2 at2

d= 1/2(-9.81m/s2)(2s)2

d= 19.62 m

d= 1/2 at2

d= 1/2(-9.81m/s2)(4s2)

d= 78.48 m (4) four times as far

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