Gravity!!!!

1. Gravity!!!!

2. Gravity • Gravity – the attraction of one mass toward another • depends on the masses of each andtheir distance fromone another • from our perspective…gravity is a constant acceleration toward the center of the earth

3. Gravity • Gravity – the attraction of one mass toward another • decreases over distance • explains why the moon has more of a gravitational effect [tides, etc] on the earth than the sun

4. Gravity – continued • Galileo Galilei • experimented to find out the acceleration of free-falling objects • showed that free-fall was constant • had difficulty showing this before using inclined planes • plane reduced force of gravity & increased distance, but with same result

5. Acceleration on Galileo’s Inclined Planes Galileo found greater accelerations for steeper inclines. The ball attains max acceleration when the incline is tipped vertically.

6. Acceleration from Gravity • Wait, wait! Why did some objects fall faster than others when we dropped them off the stadium????? • Air resistance – the friction of air particles on an object moving through it • accounts for varying speeds of falling objects

7. Air Resistance • Without air resistance, all objects fall with the same constant acceleration due to gravity

8. Recap • Galileo’s Observations: • a ball rolling down an inclined plane is moving with constant acceleration • greater accelerations for steeper planes, max acceleration when incline is tipped vertically • regardless of weight and size, when air resistance is small enough to be neglected, all objects fall with the same unchanging acceleration

9. Gravity • g = acceleration due to gravity • g = 9.8 m/s2 on earth • g will change if • the object gets farther away from the center of the earth [distance change] • the object’s mass changes [but not in relation to the earth]