## domingo, 29 de agosto de 2010

### How levers work

simple machine:a divice with few parts that makes it easier to do work

effort force: the force applied to a machine

resistance force: the force that a machine acts against

lever: a simple machine made of  a rigid bar on a pivot point

fulcrum: the pivod point of a lever

machanical advantages:the number of times a machine multiplies the force applied

pulley: a grooved wheel that turns by the action of a rope in the groove

wheel and axle: a simple machine made of a handle or axis attached to the center of a wheel

### Energy and Work

Potential energy:the energy stored in an object or material

gravitational potential energy: the potential energy of an object located above the ground

kinetic energy: the energy of an moving object

work: force applied to an object times the distance the object moves

## domingo, 22 de agosto de 2010

### Foreces and Newton´s first Law (vocabulary # 1)

Force:a push or pull exerted by one object on another

Friction:a force that opposes the motion of an object in  contact with the surface

drag force:a force that oppose the motion of and object through a liquid or gas.

gravity:a force of attraction that exist between all object with mas

net force:the combined effect  of all the forces acting on an object

balanced force: forces that cancel each other out when acting together on a single object

unbalanced force: forces that do not cancel each other out when acting together on a single object

inertia:the tendency of an object to oppose a change in motion

momentum: the mass of an object multiplied by its velocity