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Motion Unit Everyday Forces TEK: design an experiment to test the force on an object FEATURED SCIENTISTS: Albert Einstein, Sir Isaac Newton, Orville & Wilbur Wright *Force: any push or pull that causes an object to move, stop, or change direction *Friction: a force that opposes, or acts against, motion when two surfaces rub against each other a. A baseball player sliding into base feels a great deal of friction happening between his pants and the ground. He slows down and eventually stops due to friction. a b. People on a sled don’t feel much friction as they slide down hill covered with snow and ice. Since there’s not much friction, the sled gains speed the whole way down the hill. *Gravitation: the force that pulls all objects in the universe toward one another and holds things to the surface of the earth Strength of gravitationDepends on the mass of the two objects and the distance between them 1. Two ping pong balls have a small combined mass so even though they pull on each other, you can’t see them moving. 2. The earth and a human have a huge combined mass! That’s why the two pull so hard on each other. They are always in contact unless acted upon by an outside force. The increased mass means increased gravity. If the mass is small then the gravity is less. The further you get from earth the less you weigh. 1 Motion Unit *Buoyancy: a buoyant force is the upward push of a liquid or gas on an object. The Laws of Motion 1st Law An object will remain at rest, and an object will continue moving in a straight line at a constant speed until an outside force acts on it. 2nd Law An object’s acceleration depends on its mass and on the size and direction of the force acting upon it. 3rd Law For every action, there is an equal and opposite reaction. *Magnetism: a force of repulsion (pushing) or attracting (pulling) between poles of magnets a. Like magnets repel b. Unlike magnets attract (opposites attract) S N N S S N S N c. Earth is a giant magnet! The “North Pole” and the “South Pole” were named because of their magnetism. Compasses are magnets. That’s why they’re used to tell directions! 2 Motion Unit Electromagnetism: a temporary magnet created by a flow of electric current around an iron bar. *Can turn it on and off by removing the power source *Can strengthen the power of the magnet by adding more energy *Can change the polarity of the magnet. 3 Motion Unit Energy *Transformation of Energy: continuous changing of energy from kinetic to potential and back. (bouncing ball) *Law of Conservation of Energy: “Energy can neither be created nor destroyed.” Energy can only change forms. *Energy: the ability to cause change in matter 1. Kinetic Energy: energy of motion or energy in use As the ball is moving up and down, it has kinetic energy. Types of kinetic energy: mechanical, thermal (heat), electric, sound, light 2. Potential Energy: energy an object has because of where it is or because of its position As the ball changes direction to go up or down, it temporarily stops. When this happens, it has potential energy. Mechanical Light Kinetic Kinetic Rolling car T.V. Thermal Kinetic Heater Electrical Sound Solar Kinetic Kinetic Kinetic Circuit Vibrations Sun 4 Chemical potential Photosynthesis food Elastic Potential Rubber band