Inertia and Unbalanced Forces

In Tuesday's class be began by going over previous knowledge on how to draw Free-Body Diagrams. We then discussed various word problems, that allowed us to further understand how to draw and interpret free-body diagrams. After reviewing we progressed into the Law of Inertia.

Inertia, Newton's first Law of Motion, was originally derived from the ideas of Galileo. Inertia states that an object at rest will remain at rest and an object in motion tends to remain in motion, unless acted upon by an external force. More simply, objects keep doing what their doing unless acted upon by an unbalanced force. For example a stationary object is difficult to move, and a moving object is difficult to stop.

After various experiments including removing a tablecloth from under a place setting, we found inertia depends on mass.

Unbalanced Forces

Objects are typically acted upon by numerous forces simultaneously. 

• The resultant vector is called Net Force (Fnet)
• An objects velocity will remain constant if no external unbalanced force acts on it.
• If the forces acting on an object cancel out, the resultant vector is zero, and no unbalanced forces exist. Therefore the object is in equilibrium. 
• If an object is moving with a constant velocity, the net force is zero. 

The idea of unbalanced forces can be shown in the following example.

Ex. Two boys are pulling on a bear. One pulls with a force of 15N[E] while the other with a force of 10N[W]. What is the net force? 

<---10N[W]---Bear---15N[E]--->  Fnet= 5N[E]

Clarke is next!