VSV 2015

Gravity: A force of attraction Make things move….faster, slower and change direction…also gravity makes them change shape… READING: Gravity: A force of Attraction (574 – 579) Answer the 10 questions from page 579 in your notebook VSV 2015

Sir Isaac Newton VSV 2015

Why do objects fall toward the Earth, and what keeps the planets moving in the sky? The law of universal gravitation describes the relationships between gravitational force, mass and distance. ?v=jwPc0kK9VHU VSV 2015

The Law of Universal Gravitation All objects in the universe attract each other through gravitational force VSV 2015

PART 1 PART 2 VSV 2015

Distance, Mass, Fg VSV 2015

All matter has mass All matter is affected by gravity All objects experience an attraction toward all other objects Because of gravity you are being pulled right now! Why don’t you notice objects moving toward each other?. Mass is too small. Remember VSV 2015

Weightless? (NASA pictures) VSV 2015

GRAVITY is a force of attraction between objects due to their masses. WEIGHT IS A MEASURE OF GRAVITATIONAL FORCE VSV 2015

So when gravity pulls something towards the Earth, we can call this force WEIGHT (W) W = mg So when gravity pulls something towards the Earth, we can call this force WEIGHT (W) W = mg VSV 2015

So when gravity pulls something towards the Earth, we can call this force WEIGHT (W) W = mg So when gravity pulls something towards the Earth, we can call this force WEIGHT (W) W = mg N = Kg. m S 2 VSV 2015

The force of gravity you experience due to the Earth (w) is proportional to your own mass (m). w = mg The force of gravity you experience due to the Earth (w) is proportional to your own mass (m). w = mg 'g' is the gravitational field strength  the force with which gravity pulls each kilogram of mass. 'g' is the gravitational field strength  the force with which gravity pulls each kilogram of mass. What is “g”? w = mg w = (100 kg) (9.83 N/Kg) w = mg w = (100 kg) (9.83 N/Kg) W = mg W = (100 kg) (9.83 N/Kg) W = 100 x 9.83 N W = 983 N W = mg W = (100 kg) (9.83 N/Kg) W = 100 x 9.83 N W = 983 N VSV 2015

apparently weightless (pictures or animation only –not a demonstration) VSV 2015

On the Moon – Apollo 15 A heavy geological hammer and a falcon feather were dropped from the same height. They hit the lunar surface at the same time. astronaut David Scott NASA pictures VSV 2015

Very heavy boots- Why? Answers? No gravity on the Moon Weightless on the Moon To stop them floating away They weigh very much less than on Earth To stop huge bounces The Moon’s gravity is very much less than the Earth’s gravity VSV 2015

GRAVITY Things fall Things have weight Things stay in place No Gravity Would an apple fall? Would things stay on earth? What would happen? What? Why? How? VSV 2015

“If Wile E. Coyote and a boulder fall off a cliff at the same time, which do you think will hit the ground first?” VSV 2015

two objects dropped at the same time GALILEO GALILEI VSV 2015

GRAVITY AND ACCELERATION Objects fall to the ground at the same rate because the acceleration due to gravity is the same for all objects. VSV 2015

ACCELERATION DUE TO GRAVITY It means that every second that an object falls, the object’s downward velocity increases by 9,8 m/s² All objects accelerate toward Earth at a rate of 9,8 m/s² VSV 2015

Velocity of a falling object: Δ V = g x t ΔV = final velocity – starting velocity (m/s) g = acceleration due to gravity (9,8 m/s²) t = time the object takes to fall in seconds SOLVE MATH FOCUS EXERCISES (PAGE 591 IN YOUR COPIES ) VSV 2015

Net Force = 0 N A stops Constant velocity X X Only gravity is pulling the object down VSV 2015

AN ELEPHANT AND A FEATHER Suppose that an elephant and a feather are dropped off a very tall building from the same height at the same time. Which object - the elephant or the feather - will hit the ground first? VSV 2015

As air pressure decreases, the potential for air resistance also decresases. VSV 2015

WHAT’S ORBITING?  AN OBJECT IS ORBITING WHEN IT IS TRAVELING AROUND ANOTHER OBJECT INTHE SPACE Orbiting and free falling VSV 2015

Launching a satellite The cannon ball must move very quickly to orbit the earth. The Moon orbits the Earth VSV 2015

THIS MOTION IS A CURVED PATH WHEN IT IS THROWN OR PROPELLED NEAR THE SURFACE OF THE EARTH MOTION PARALLEL TO THE GROUND MOTION DOWNWARD VSV 2015

READING: Gravity and Motion(590 – 597) Answer the 10 questions from page 597 in your notebook HOMEWORK VSV 2015