1. Net Force (Free Body) Diagram. Newton’s Second Law

2. Force

3. Friction Forces Friction Forces are forces that act on materials in contact with one another Friction acts in the direction opposite to motion. Constant velocity = frictional force balances out the applied force, net force equals zero Fluid friction applies to liquids and gases. Most common is air resistance.

4. Friction Forces

5. Net Force Net Force is combination of all forces acting on an object (normal force, applied force, frictional force, and force of weight). When net force is equal to zero, either the system is at rest or there is constant velocity (no acceleration). No acceleration means there is no change in velocity. Fn F applied F friction Fw Text book Wood block

6. Forces

7. Equilibrium Equilibrium is the state of an object (or system) in which there is no change in motions (at rest or constant velocity) Fn y Fapplied F friction F w x Free body diagram textbook

8. Equilibrium Equilibrium: equations which describe the relationship among opposing forces directed along the x and y axis. ∑ Fx – the sum of the forces in the x direction ∑ - sigma, “the sum of” ∑ Fx = right – left ∑ Fy – the sum of the forces in the y direction ∑ Fy = up – down

9. Net Force (Free Body) Diagram Problem. A jug of juice is resting on the table when a rightward force of 25 N is applied. The force of friction is 10 N. The weight of the juice is 7 N. Draw a free body diagram and write equilibrium statement. ∑ Fx = right – left y ∑ Fx = 25 N – 10 N ∑ Fx = 15 N x ∑ Fy = up – down ∑ Fy = 7 N – 7 N Fapp = 25 N Fn = 7 N ∑ Fy = 0 N Ff = 10 N table Fw=7Ns juice

10. Acceleration and Force

11. Mass and Acceleration

12. Newton’s Second Law of Motion

13. Newton’s Second Law of Motion Examples 3 kg 6 kg

14. Newton’s Second Law of Motion Examples