Gravity Notes What is a Gravity First described

Gravity Notes

What is a Gravity? ¡First described by Isaac Newton ¡Observed an apple fall from a tree straight to the ground ¡Concluded an invisible force was pulling the apple toward Earth

What is a Gravity? ¡Gravity = a force that pulls objects toward one another ¡All objects exert a gravitational pull on one another ¡The one we experience the most is Earth’s gravitational pull

What factors affect gravity? ¡Gravity is not unique to Earth ¡Universal gravitation ¡A force of gravity exists between all objects in the universe ¡All objects attract one another

What factors affect gravity? ¡Sometimes we feel this attraction and a lot of times we don’t…WHY? ¡Two factors affect gravitation attraction between objects: Mass and distance.

What factors affect gravity? Distance ¡As distance increases between 2 objects, the attraction becomes weaker. ¡As distance decreases between 2 objects, the attraction becomes greater.

What factors affect gravity? ¡Mass ¡Objects with greater mass have greater gravitational force

What factors affect gravity? ¡Why are we pulled to the Earth and not the other way around? ¡Earth has a much greater mass and so a much stronger gravitational pull.

What factors affect gravity? ¡Why do the planets orbit the sun? ¡The sun’s mass is so great that its gravitational pull is strong enough to keep the planets locked in place.

Weight ¡Mass = amount of matter in an object ¡Weight = force of gravity on an object ¡Weight changes with gravity but mass does not!

Imagine Miss Falk on different planets: Weight on Earth = 110 lbs Venus = 90% Earth’s gravity _______l bs. 99 Mars = 38% Earth’s gravity _______l bs. 42 Jupiter = 250% Earth’s gravity _______l 275 bs.

What is a Free Fall? ¡When you hold a book in the air it does not fall Hand = 50 N ¡Gravity pulls down ¡Your hand pushes up ¡Net force = 0 N = no movement Gravity = 50 N

What is a Free Fall? ¡When you let go it falls ¡Gravity pulls down ¡No other force acts ¡Net force = 50 N down = movement down Gravity = 50 N

What is a Free Fall? ¡Free fall = when gravity is the only force acting on an object ¡This causes objects to accelerate downward ¡Acceleration due to gravity = 9. 8 m/s 2

What is a Free Fall? ¡Example: It takes 5 seconds for a book to fall to the floor. If acceleration due to gravity is 9. 8 m/s 2, what speed did the book reach before hitting the ground? S=A(T) = 9. 8 m/s 2 (5 s) = 49 m/s S A T

What is a Free Fall? ¡All objects, regardless of size or mass, fall at the same acceleration rate.

Feather and Hammer Drop ¡Which would hit the ground first? ¡Why? ¡Hammer vs. Feather ¡Feather and Ball bearing

Air resistance ¡In real life, some objects fall faster than others. ¡Ex: A basketball falls faster than a leaf. 5 seconds Gravity = 10 N 2 seconds

Air resistance? ¡This is due to air resistance Air Resistance ¡Fluid friction against the object ¡Some objects are more aerodynamic than others. Gravity

Air resistance ¡If air resistance becomes great enough, it equals the force of gravity ¡This results in balanced Air resistance forces =100 N ¡Acceleration stops ¡The objects stays at a constant speed = terminal velocity Gravity pull=100 N

https: //www. youtube. com/watch? v=3 o. Iak. Jek. CZU

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