Review- What is happening in this video? How?

1. Review- What is happening in this video?How? http://player.discoveryeducation.com/index.cfm?guidAssetId=69D515CC-CFDF-4DB2-9F6D-386F68CD4E02&blnFromSearch=1&productcode=US#

2. Objectives • Review- Entrance Ticket. • Weight Vs. Mass • Distinguish between force and net force. • Equilibrium rule.

3. Force of gravity acting on an object http://www.exploratorium.edu/ronh/weight/index.html Amount of Matter an object contains Weight VS. MASS

4. What is Force? • Force is a Push or a Pull • Forces are vector quantities - they have a magnitude (How Much) and a direction • Ex.: 10 N to the right • Forces are shown with arrows • Point in the direction which it is being applied. • The length of the arrow shows the magnitude (how much) of the force.

5. Net Force (Unbalanced Force) • Total force being exerted on an object. • Ex. Pull a box w/ net force of 5 N, • A Friend pulls a box w/ net force of 5 N • How much total force is being pulled?

6. Net Force • If no forces act on an object, the net force on the object is zero. • Additional Examples- • http://www.batesville.k12.in.us/physics/phynet/mechanics/newton1/the_net_force.html

7. Net Force Activity

8. Normal Force • The force on an object that is in contact with a surface • It is perpendicular to the surface • It usually is the force opposite of the weight of the object.

9. Equilibrium • When the net force on something is zero: • That something is in mechanical equilibrium. • What is equilibrium? • Equilibrium means a state of physical balance.

10. Equilibrium • Equilibrium Rule: • ∑ F = 0 • ∑ stands for the “vector sum of” • F stands for “forces”

11. Equilibrium • Equilibrium Rule Continued: • The rule says that the forces acting in one direction on an object must be balanced by forces acting in the opposite direction. • Example: Forces acting upward must be balanced by forces acting downward. • In essence, they must cancel each other out.

12. Static Equilibrium • Static means “not moving.” • If an object is not moving, it is in static equilibrium • This means that the weight of the object is canceled out by the normal force.

13. Dynamic Equilibrium • Dynamic means “moving.” • An object is in dynamic equilibrium when it is moving with a constant velocity. • Example – The force applied to the car is equal to the friction acting against it.