FORCES & Newton!

FORCE A force is any push or pull, and it can be balanced or unbalanced (force is measured in Newtons (N)).

Net Force The combination of ALL forces acting on an object…which can be ◦Contact – when force is exerted b/c one object is touching the other ◦Non Contact – when force is exerted when objects aren’t even touching!

Forces (cont.) When the net force is zero, the forces on an object become a balanced force. If the net force is not zero, then the forces on an object become unbalanced forces.

Contact Forces Inertia is the tendency of an object to resist a change in motion. A force exerted only when two objects are touching each other is called a contact force. Friction is a force that opposes the relative motion of two surfaces that are in contact.

Contact Forces (cont.) Tension is the magnitude of the pulling force exerted by a string, cable, chain, or similar object on another object. The opposite of tension is compression, since it is the pushing or pressing force that is directed toward the center of an object.

Contact Forces (cont.) Air resistance is the friction from air molecules hitting an object as the object moves through the air, opposing the motion of objects moving in Think of when you ride a bike. Do you feel the air resisting against your movement?

Centripetal force is a force that makes a body follow a curved path: it is always directed perpendicular to the velocity of the body, toward the instantaneous center of curvature of the pathcenter of curvature For a satellite in orbit around a planet, the centripetal force is supplied by gravitysatelliteorbitplanet

Non-Contact Forces A non-contact force is when a force has been exerted even though the objects are not touching each other. ◦Examples:  electrical  magnetic  gravitational

Non-Contact Forces (cont.) An electrical force is a push or pull that is exerted on an electrical charged objects. Think of positive protons and negative electons.

Static Electricity Static electricity is the charge that stays on an object. Unlike charges attract each other, and like charges repel each other.

Non-Contact Forces (cont.) A magnetic force, works pretty much the same way. It is basically an attraction or repulsion of a magnetic material due to the arrangement of its atoms, particulary its electrons.

Non-Contact Forces (cont.) Gravity is the pull that every object always exerts on every other object due to their masses. A gravitational force exists between any two objects that have mass. Therefore, it completely depends on the objects mass and the distance.

Calculating Net Force So, now that we know all the possible forces that can act on an object; I can figure out the Net Force (let’s visualize) ◦----  >5= ◦---   --- = ◦--   10 = ◦--  5 +  =

Newton! Newton’s First LAW of Motion: (Inertia) if an object’s net force is 0; it will remain at rest (0); if an object is in motion; it will remain in motion, at a constant speed, until a force acts on it!!!! ◦In English: The velocity of an object doesn’t change if all its forces are balanced! (Only Unbalanced forces can cause a change)