Here we look at Newton's three laws of motion starting with inertia, then force causes acceleration, and lastly action reaction pairs.  In this section we will look at the difference between mass and weight.  Then look at additional forces like air resistance, friction, and ones created on an incline plane.

1: Newtons First Law: Inertia

The first law of motion is about inertia.  An objects resistance to a change in motion.  An object in motion stays in motion and an object at rest stays at rest.  So this the state of motion wont change unless acted upon by an outside force.

2: Newton's Second Law: Net Force Causes Acceleration

Force alone does not cause a change in motion if balanced by another.  When there is a non-zero net force an object will accelerate.


3: Mass and Weight

Mass is determined by the molecular composition of an object.  Weight is a force created by the pull of an object towards another like the earth.  Learn the difference and see how to use the weight equation (Fw = mg) here.

4: Newton's Third Law: Action Reaction Pairs

No force in the universe is ever created without an equal and opposite reaction force.  Learn about action reaction pairs and the accelerations that result from these.

5: Forces: Friction

Frictional force is created because objects on some level are rough.  When surfaces rub against each other a frictional force is created that resists this motion.

6: Forces: Air Resistance

Air is made of particles.  The faster you go through air the more particles you hit creating an air frictional force opposing the motion.

7: Tension Force

When a rope is pulled an equal and opposite force called tension is created by the stretch in that rope.  See how to approach a variety of tension problems here.

8: Hooke's Law and Spring Force

When you pull a spring a force is created in the opposite direction of the pull.  Hooke's Law (Fspring = -kx) relates the type of spring to the force required to displace it.

9: Forces on Incline Planes

The weight of an object on an incline plane creates forces that push into the hill and down the hill along with many others.  Learn how to determine these forces and an objects acceleration on an incline plane.

10: Forces Unit Assessment Page

See all the forces section assessments all in one place.  Assess yourself to see if you are ready for your forces test.