A Force is simply a push or a pull on an object A Force is simply a push or a pull on an object. But, an object can’t be pushed or pulled by itself, so force requires at least 2 objects. Like velocity and acceleration, distance is also taken into consideration along with strength when describing and calculating force. Forces are exerted on objects all of the time….Gravity, Electromagnetism, an Atom’s Nucleus – all these things exert forces on the objects in our universe. Also like velocity, when forces act in the same direction we add them. When they act in opposite directions, we subtract. Notice that force is measured in units called “Newtons”. When all forces are combined, we call this the “Net” force. “Balanced” forces produce a net force of Zero Newtons – the object doesn’t move! Otherwise, the force would be “unbalanced” and the object would move.

What 2 forces are acting on the shuttle? Would a space shuttle taking off represent a balanced force or an unbalanced force? (otherwise, it wouldn’t “take off”!) What 2 forces are acting on the shuttle? (Gravity and the burning rocket propellant) The Net Force is acting in which direction? Up In the situation of a parachute, a force called Friction is purposely increased to counteract the force of gravity in the opposite direction. The net force is still unbalanced, but only enough to make sure you hit the ground while staying in one piece.

Kakashi will be pushed out of the ring first! The sumo wrestler on the left (Sasuke) is exerting a force of 32 Newtons North, while the wrestler on the right (Kakashi) is exerting 29 Newtons of force in a Southern direction. Which wrestler will get pushed out the ring first? What will be the combined net force? Is this a balanced or unbalanced force? Kakashi will be pushed out of the ring first! The resulting net force will be 3 Newtons North. This is an example of an unbalanced force. Bill and Ted are moving a couch. Bill is pushing the couch west with 11 Newtons of force while Ted is pulling the couch in the same direction (west) with 8 Newtons of Force. What is the Net Force? Is this a balanced or unbalanced force? The resulting net force will be 19 Newtons west. This is an example of an unbalanced force. H o w s t r o n g o f a f o r c e i s g r a v i t y ? The Earth has a mass of six million billion billion kilograms, and yet its gravity isn't enough to overcome the magnetic force generated by a magnet whose mass is a small fraction of one kilogram. Think about this the next time you hang up an A+ test on your fridge for all to see!

Gravity is only one type of force, but it is an important one. Gravity Facts: *Anything that has mass affects gravity. *It is a force of attraction. *It effects the velocity of objects on both a large and small scale *Gravitation increases as mass increases. *Gravitation decreases as distance increases *It keeps you on the Earth, the Moon in orbit around the Earth, and the Earth (and other planets) in orbit around the Sun. *It is an invisible force, but it’s effects can be seen. *It was described first by Sir Isaac Newton around 300 years ago. How does gravity work though… Something with mass bends the space-time fabric in 3 dimensions (like illustrated in just 2 dimensions below.) thus causing objects to “fall” around them.

Which one of us is lying? A Mosquito buzzing around you has a greater gravitational pull on your body than the moon does. Anne Astronauts in orbit are still in strong Earth gravity. They are weightless not because of a lack of gravity, but because they are in free fall, constantly falling around Earth. Brent If you were on the largest asteroid in our solar system, Ceres, and you threw a rock as hard as you could, it would go into orbit. Cal Gravity doesn’t stop in outer space; it keeps going forever. Gravity can reach so far, it can pull entire galaxies together and cause them to collide. Donna Isaac Newton came up with the idea of gravity after a falling apple struck him in the head. Erik Astronauts grow several inches out in space without the force of gravity pulling them down, but back on Earth they shrink back to their original Earth height. Fay

Caution: Brains at work: Mass vs. Weight In physics, the terms mass and weight do not mean the same thing. As you know, mass refers to how much matter makes up an object. Weight however, refers to the force that which something is pulled downward. Therefore, weight is very dependant on gravity, whereas mass is not. Example: Here on Earth, if I asked you to find the mass of a rock, you would put in on a scale. Let’s say it weighs 100 grams. Repeat the same experiment on the moon – a place that only has a fraction of the Earth’s mass. Remember, less mass means less gravity. The rock would have the same mass no matter where you took it in the universe, but because the moon has 1/6 the gravity of Earth, it is not being pulled down to the surface with as much force. It wouldn’t weight 100 grams as it did on Earth, but only 17 grams! Caution: Brains at work: Distance too, not just mass effects gravitation: Gravity at the equator is slightly less than at the North Pole, because the Earth bulges at the equator and you are further from the center of the Earth. If you buy gold by carat weight on the equator and sell it on the North Pole, you could make a small amount of profit -- minus traveling expenses, of course!