Gravity

Law of Universal Gravitation The force of gravity applies to everything in the universe The force of gravity applies to everything in the universe It can be calculated using the formula: It can be calculated using the formula: F= G(M 1 M 2 /d 2 ) F= G(M 1 M 2 /d 2 ) G is the constant of universal gravity G is the constant of universal gravity M is the mass of each object M is the mass of each object D is the distance between them D is the distance between them

Properties of Gravity Gravitational force increases as mass increases Gravitational force increases as mass increases the sun’s gravitational force is 28 times that of that of Earth. the sun’s gravitational force is 28 times that of that of Earth. Gravitational force decreases as distance increases Gravitational force decreases as distance increases Pair share Pair share: A explain to B (using the law of gravity) why the moon orbits the Earth and not the sun.

Free fall When gravity is the only force acting on a object the object is the free fall When gravity is the only force acting on a object the object is the free fall The free fall near the Earth’s surface is constant The free fall near the Earth’s surface is constant 9.8m/s 2 9.8m/s 2 Pair share Pair share: B explain to A why both the mouse and elephant hit the ground at the same time.

Weight Weight is equal to mass times free-fall acceleration Weight is equal to mass times free-fall acceleration Weight = Mass x free-fall acceleration (W=mg) Weight = Mass x free-fall acceleration (W=mg) Weight is less when gravity is less Weight is less when gravity is less MERCURY The Same person who weighs 49 lbs on Mercury would weigh 307 lbs on Jupiter JUPITER

Terminal velocity Terminal velocity is when air resistance and gravity are equal Terminal velocity is when air resistance and gravity are equal Air resistance pushes up on falling objects Air resistance pushes up on falling objects

Free fall and motion Free fall exists only when gravity is the only force acting on an object Free fall exists only when gravity is the only force acting on an object Free fall only occurs in a vacuum Free fall only occurs in a vacuum The earth orbits the sun because of free fall The earth orbits the sun because of free fall An orbit is when an object moving forward is also in free fall An orbit is when an object moving forward is also in free fall

Projectile Motion and Gravity Projectile motion is the curved path that an object follows when thrown Projectile motion is the curved path that an object follows when thrown The object is moving in two directions at once – forward and down The object is moving in two directions at once – forward and down The forward motion is a constant velocity, not effected by the downward pull of gravity The forward motion is a constant velocity, not effected by the downward pull of gravity Whiteboard Whiteboard : Would the motion of a ball thrown with the same force on the Earth and moon have the same motion? Explain.

White board Review 1) As mass increases what happens to gravitational force? 2) What 2 things are need to calculate weight? 3) Objects have an orbit because of their forward motion and _____________.

Summary - Read over your notes then write In 4 sentences describe the properties of gravity & how they relate to weight & projectile motion.