• Turn in completed Friction Lab to the front.
• No need to staple, you will get it back within the class period.

• Calculate weight of an object & explain why it changes on different planets.

• On page109

• Do you ever feel like life is weighing you down - that life is hard?
• Well… you’re not alone and the reason you feel weighed down is the same for everybody.
• It’s called gravity!

• Gravity is the force that pulls objects towards each other.
• Universal Law of Gravity
All objects in the universe are attracted to each other through gravitational force.
– The bigger the mass, the greater the gravity
(and vice versa)
– The closer the objects are, the greater the gravity (and vice versa)

• Mass is the amount of matter in an object. It’s constant, it never changes
• Weight is mass times gravity
(W=m X g)
• Why is weight different depending on where you are in the universe.

• Galileo proposed that all objects will land at the same time when they are dropped at the same time from the same height.
• Acceleration due to gravity =
9.8 m/s/s
• Falling fast?? A falling object’s speed increases by 9.8 m/s for every second that goes by.
– 1 second = 9.8 m/s
– 2 seconds = 19.6 m/s
– 3 seconds = 29.4 m/s

• Air resistance affects all objects differently.
• Terminal velocity = moment when acceleration due to gravity stops because of air resistance.
– Human – 80 m/s (120 mph)
• 100 m/s bullet shape (200 mph)
– Penny – 50 m/s
• Free fall occurs when there is no air resistance.
Only gravity is accelerating the object downward.
• Can you ever reach true free fall on Earth?

• The curved path an object takes when it is propelled near the surface of the Earth.
• Draw the picture to the right and label horizontal and vertical motion of the baseball

• http://ed.ted.com/l essons/jonbergmann-howto-think-aboutgravity