| A | B |
|---|
| force | push or a pull |
| balanced forces | forcesthat are equal in size but opposite in direction |
| unbalanced forces | forces that cause a change in the motion of an object |
| What are 2 ways that unbalanced forces can change the motion of an object? | 1.when an unbalanced force acts on an object at rest, the object will move 2.the motion of the object will change, it may speed up, slow down, stop moving or change direction |
| What are forces found in nature? | weight, magnetic force, wind, and falling water |
| Sir Isaac Newton | he hypothesized that there is a force that makes all objects move toward each other |
| Newton's law of gravity or universal gravitation | All objects in the universe are attracted to one another because of the force of gravity between them |
| gravity | force of attraction between all objects in the universe |
| What does the gravitational force between two objects depend on ? | the mass of each object |
| When does the force of gravity decrease? | as the distance between them increases |
| newton | basic SI unit of force- on Earth it takes 9.8 N to lift 1 kg mass |
| weight | the pull of gravity on an object |
| spring scale | is used to measure weight |
| What other types of spring scales are there? | bathroom scale and grocer's scale |
| How does a spring scale work? | attach a mass to the hook, the mass stretches the spring and the pointer moves down along the scale. The number at which the pointer stops is the object's weight |
| friction | a force that opposes the motion of an object |
| What are the types of friction? | static friction, sliding friction, air resistance |
| Why is friction useful? | On Earth friction makes motion possible ex. riding a bike, walking, throw a ball, hold a pencil, kites, birds and airplanes fly |
| What is harmful friction? | Is found in machines and engines. The metal parts that move against each other produce heat and can cause parts to wear out |
| What do you need to overcome the force of friction? | a larger force |
| How can you reduce friction? | to change sliding friction to rolling friction, and lubricants |
| lubricants | materials that reduce friction ex. oil |
| How can you increase friction? | spread sand on ice, special footwear, |
| air resistance | force that opposes the movement of an object in air |
| energy | ability to make something happen |
| potential energy | stored energy |
| kinetic energy | energy of motion |
| mechanical energy | the energy in moving things |
| electrical energy | energy of moving electrons |
| electromagnetic energy | energy that can travel through a vacuum ex.visible light, X-rays, radio waves, microwaves |
| heat energy | the energy of the moving particles that make up matter |
| chemical energy | the energy that holds particles of matter together |
| nuclear energy | energy stored in the nucleus of an atom |
| thermal pollution | damage that occurs when waste heat enters the environment |
| law of conservation of energy | energy cannot be made or destroyed, but only changed in form |
