1. Acceleration due to Gravity CCHS Physics

2. Historical Background

3. Galileo attempts to prove Aristotle’s hypothesis wrong… He drops objects of various weights from the Leaning Tower of Pisa and compares the falls. He thinks that light and heavy objects will fall at the same rate. We’ll find out who is correct with a demonstration…

4. Let’s See The Real Thing

5. So who’s right? Both- why? In the absence of air resistance, all objects accelerate towards Earth at the same rate. We call this “free-fall” acceleration- meaning gravity is the only force acting on an object. Because we use this value so often we’ll give it a name- g What do you think g depends on?

6. For an object in free-fall, g depends on… Mass of the planet object is near Distance from object to the center of the planet ( G = universal gravitational constant) Near the surface of the Earth, g = -9.8 m/s 2

7. Free Fall Motion of a body when only the force of gravity is acting on the body The acceleration of an object in free fall is called the acceleration due to gravity, or free fall accleration Free fall acceleration is denoted by the symbol g

8. Free Fall Movie

9. Handy Chart

10. Velocity and Acceleration Movie

11. Let’s try some examples Estimate the following: A stone is dropped off a cliff. What is its velocity 5 seconds later? A ball is tossed straight up at 30 m/s. How long will it take to land? (It returns to same height.)

12. Let’s try some more … a little harder though Ms. Clark throws a ball straight down off a building with an initial speed of 10 m/s. It lands 3 seconds later. How high was the building?

13. One More Example Jason hits a volleyball so that it moves with an initial velocity of 6 m/s straight upward. If the volleyball starts from 2 m above the floor, how long will it be in the air before it strikes the floor? –Choose origin to be initial position of ball –The displacement of the ball is -2 m