Linear MotionUnit 1 Part II

Forces

Objectives:

• State Newton’s 1st law of motion and display an understanding of its applications

• Understand the difference between net forces that cause acceleration and those that have a zero acceleration

• Identify action-reaction pairs• Be able to use the equilibrium rule with forces

Newton’s 1st Law

Isaac Newton- History: 1665 started working on laws of motion, but

not published until 1687

**Newton’s First Law** (Law of Inertia)An object in motion/rest stays in motion/rest until

acted upon by an external force.

Inertia

Inertia-

Ex pg. 28: A hockey pucks sliding across the ice finally comes to rest. How would Aristotle have interpreted this behavior? How would Galileo and Newton have interpreted it? How do you interpret it?

Net ForceNet Force- Forces are exerted ON a body (Action) and is exerted BY another body (Reaction).Hammer/Nail Person/Grocery Cart

Table/Book Box/Boat(vi = 0 m/s)

The Equilibrium Rule

If there is no movement on an object it is said to be at equilibrium.

OR if the object is maintaining a constant velocity (speed) it is at equilibrium.

Equilibrium of Moving Things

Rest is only 1 form of equilibrium. An object at constant SPEED/VELOCITY is also at EQUILIBIRUM!!! At constant speed an object has NO net forces acting on it.

The Moving Earth

Copernicus’s idea that the Earth was moving was a debated topic. Early estimates were that the Earth was moving 107,000 km/hr or 30 km/s to encircle the Sun.

True/False. If a bird were to drop to get a worm in 1 second from 30 km away it would miss the worm. Why?