Notes

Force

Force• Force is a push or pull exerted

on some object.• Forces cause changes in velocity.• The SI unit for force is the

Newton.• 1 Newton = 1 kg m/s2

2 types of forces• Contact Force – physical

contact between two objects• Field Force – does not

involve physical contact between two objects. Example is electrical forces

Balanced Forces• Forces that are equal in size

and opposite in direction

Net Forces• A force on an object that changes the

velocity of the object.

• The object accelerates in the direction of the greater force.

• A net force acting on an object will change its speed, direction or both.

Friction

• The force that opposes motion between two surfaces that are touching each other.

• Without friction, an object in motion would keep moving forever.

• Friction opposes the motion of any object.

Inertia

• The resistance an object has to a change in its motion.

• A body at _______ will remain at ______ and a body in ________ will keep moving unless a force acts on it.

Newton’s First Law

• Also called the Law of Inertia or First Law of Newton.

• An object in motion or at rest will stay in motion or at rest unless acted upon by a net force.

Normal Force• Every object has an equal and

opposite force.• The weight is the first and most

obvious force.• However, the equal and opposite

force is called the normal force.• Normal force is always 90 degrees

to the horizontal.