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.

b.  People on a sled don’t feel much friction as they slide down a 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 gravitation-

Depends 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.

*Buoyancy: a buoyant force is the upward push of a liquid or gas on an object.

The Laws of Motion

1st Law / 2nd Law / 3rd 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. / An object’s acceleration depends on its mass and on the size and direction of the force acting upon it. / 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)

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!

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.

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

·  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

Mechanical / Light / Thermal / Electrical / Sound / Solar / Chemical / Elastic
Kinetic / Kinetic / Kinetic / Kinetic / Kinetic / Kinetic / potential / Potential
Rolling car / T.V. / Heater / Circuit / Vibrations / Sun / Photosynthesis food / Rubber band

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