1. Dynamics This is the branch of mechanics that deals with how the forces acting on an object affect its motion. The physical laws that govern dynamics were formulated by Isaac Newton.

2. Answer Me!!! Describe what you know about Newton’s Three Laws of Motion.

3. Newton’s First Law Law of Inertia An object will maintain its state of equilibrium (either at rest, or moving at a constant velocity) unless acted upon by an unbalanced force.  An unbalanced force is a nonzero net force acting on an object.  This unbalanced force will always produce a change in the object’s velocity vector. Inertia is the resistance of an object to a change in that objects motion. 

4. Practice Problem Which object has more inertia?  A student sitting at her desk  A football in flight  A penny falling from the Empire State Building  A paper being crumpled

5. Newton’s Second Law When an unbalanced force acts on an object, the object is accelerated in the same direction as the force.  The acceleration is directly proportional to the magnitude of the unbalanced force and inversely proportional to the object’s mass.

6. Newton’s Second Law cont. Mass is measured in kg. Acceleration is measured in m/s 2 Therefore, 1N = 1 kg*m/s 2

7. Practice: A 13 kg object is pushed with a force of 60N across a frictionless surface. What is the magnitude of the object’s acceleration?

8. Newton’s Third Law When one object exerts a force on a second object, the second object exerts a force on the first that is equal in magnitude and in the opposite direction.  For every action, there is an equal and opposite reaction.  There is no such thing as a single force, they are always generated in opposing pairs.

9. Practice Problem Draw two separate free-body diagrams for 1kg mass and the.5kg mass. Identify the opposing pair of forces in the two free body diagrams. 1 kg.5 kg

10. Final Thought… A 200 N force was applied to 10 kg chair for 15 seconds. If the chair was originally at rest, how fast was the chair moving at the end of 15 seconds?

11. Answer Me…. The diagram show two forces F 1 and F 2 applied to a 2.0 kg box originally at rest on a horizontal, frictionless surface. Calculate the magnitude and direction of the acceleration of the box. 2.0 kg F 1 = 3.0 NF 2 = 10.0 N

12. Answer Me!!! The diagram show two forces F 1 and F 2 applied to a 2.0 kg box originally at rest on a horizontal, frictionless surface. Calculate the magnitude and direction of the acceleration of the box. 2.0 kg F 1 = 3.0 N F 2 = 10.0 N 30 o

13. Answer Me!!! A 300 kg block is placed at the top of a frictionless incline that is 5 meters long along the incline and has an angle of 20 o. Calculate the time to reach the bottom.