Newton’s Laws of motion

Forces

• We have talked about different forces before but haven’t examined them in depth.

• A force is a push or a pull on an object

• What are some forces that act on you?

Contact vs. range force

• A contact force is a force exerted when it is in contact with something else

• A range force is a force exerted without making physical contact with another object

Free body diagrams

• Free body diagrams are drawings that show all of the forces acting on a body (object)

• In your groups draw 5 free body diagrams of objects in our class.

Free body diagram of a moving object

• As Mr. Gehlsen rolls the ball find the free body diagram of the ball.

Free body diagrams

• What if 2 forces acted on an object in the same direction?

Net force

• Net force is the vector sum of all forces acting on an object

• When net force is zero an object isn’t moving: this is called equilibrium

• What happens when a net force is not zero?

Newton’s Second Law

• The vector sum of the external forces F on an object is equal to the mass m of that object multiplied by the acceleration vector a of the object: F = ma.

Units of force

• What is the unit of force in basic units

Newton’s First Law

• When viewed in an inertial reference frame, an object either remains at rest or continues to move at a constant velocity, unless acted upon by an external force.

Newton’s First Law

• An object will stay at rest or continue to move unless an outside force acts on it.

Inertia

• Inertia is the tendency for an object to resist change.

• What are some objects that resist change?