Gravity- I’m Attracted to You S8P5. Students will recognize characteristics of gravity, electricity, and magnetism as major kinds of forces acting in nature. a. Recognize that every object exerts gravitational force on every other object and that the force exerted depends on how much mass the objects have and how far apart they are. (DOK 1)

Gravity ► The force of attraction that exists between all matter in the universe.  Key word is matter  Matter is the stuff you are and everything else is made of ► It takes a lot of mass for the gravity to be noticeable.  Like planetary mass

Law of Gravity ► The force of attraction between any two objects depends on their masses and the distances between them.  The bigger the object, the more gravity it has  The closer an object is to something the stronger the pull.

Mass ► Mass is how much matter is in something. ► It is measured using grams and kilograms ► It is NOT the same as weight

Distance ► Gravity’s force depends on how close the object is to something. ► As an object gets further away, the force of gravity on that object decreases ► Inverse square law  As the distance increases the gravity decreases exponentially ► Class demonstration

Gravitational force = 1 Distance squared G force = 1 d2d2

Weight, Mass, and Gravity ► Weight and Mass are not the same thing!!! ► The are related though ► Weight is your mass being pulled down by gravity ► Gravity on earth pulls us down at 9.8 m/s 2

Weight, Mass, and Gravity Mass ► How much matter you are made of ► Does not change depending location ► It is the same if you are on earth or in space or on the moon Weight ► The relationship between mass and gravity ► Changes depending on location ► Is different on earth and the moon and space

► In the absence of air resistance, all things will fall toward the earth at the same velocity same velocitysame velocity ► Weight = mass x free-fall acceleration ► w= m g

Find Your Mass ► We can find out how much mass we have by using the previous formula ► W = mg ► Weight is in Newtons, so convert your lbs to N.  Multiply lbs times ► Then divide by gravity

Gravity on Earth ► Gravity pulls us down toward the center of the earth. ► At different parts of the earth there is more matter between the surface and the center. ► The Poles are flatter and the equator bulges  The bulge means there is more gravity at the equator  People weigh more at the equator than the poles.

Gravity & the Moon  Newton observed the Moon’s motion and realized that its direction changes because of the gravitational attraction of Earth  The Moon is constantly falling toward Earth  If no gravity, the Moon would continue to move in a straight line and would not orbit Earth  The same is true of the planets and their moons, stars, and all orbiting bodies throughout the universe.