Free fall Definition: movement under the force of gravity only

Gravity Definition: the force that attracts a body toward the center of the earth, or toward any other physical body having mass When you drop an object, gravity starts pulling it down Acceleration due to gravity is always down toward the center of the earth Acceleration due to gravity represented as “g” and is equal to….

The wonders of free fall In the absence of air resistance, all objects fall at a constant acceleration, regardless of their size or weight. a or g = -9.8 m/s2

The acceleration is the same at all points – only the velocity changes. Even though the velocity is zero at the top of the ball’s flight, its acceleration is still -9.8 m/s2. If you know the initial velocity at which the ball was thrown, you can calculate how fast it is going and how far it goes at any point during its flight.

So let’s say the ball was thrown with an initial velocity of 10. 5 m/s So let’s say the ball was thrown with an initial velocity of 10.5 m/s. How fast was it going after 1 s?

Ex 1 While watching the DHJ football team play at Farrington Field, I accidentally dropped my cell phone from my seat at the top of the bleachers. I heard it crack 3.3 seconds later. How high up was my seat?

Ex 2 A ball is thrown vertically upward with an initial velocity of 19.5 m/s. What is the maximum height reached by the ball?

Ex 3 A 30 lb weight falls freely from rest from the roof of a building. What is the total distance the weight falls after 3 seconds?

CHALLENGE QUESTION David throws a baseball into the air at 10 m/s. How long will it be before the baseball comes back and hits him in the head?

Closing Question Knowing what you know about free fall, predict what the position vs. time graph and velocity vs. time graph would look like for an object in free fall?