4. “Law of Acceleration”

9. Forces can be BALANCED or UNBALANCED Balanced forces are equal in size (magnitude) and opposite in direction UNbalanced forces are not equal in size (magnitude) and/or opposite in direction. If the forces on an object are UNBALANCED, we say a NET force results. What is a Force?

10. GRAVITY GRAVITY: An attraction force between all masses force The greater the mass, the greater the force Acceleration due to gravity = 9.8 m/s/s or 9.8 m/s 2 What is Gravity?

12. Weight (F g ) is a measure of the gravitational force between two objects The greater the mass the greater the force (weight) Measured in units called newtons (N)

13. Air resistance : The force of air exerted on a falling object The air pushes up as gravity pulls down Dependent upon the shape and surface area of the object and its speed When the air resistance magnitude equals the force of gravity magnitude, terminal speed is reached Terminal speed is the highest speed that an object will reach as it falls freely in air

14. Terminal Velocity

15. What is Friction?

16. The force of friction The push things give to each other when they rub together. This changes motion into heat. Friction is the force that acts in the opposite direction of motion of the object In Newton’s world, if you could eliminate friction, then you would see more things keep on moving in a straight line. Newton’s first law only makes sense when all forces, including friction, are accounted for.

17. Tension A pull exerted by a rope, string, cable, etc.

20. Free Body Diagrams

21. FBD Practice #1 A rock is dragged rightward by a string speeding up across a rough surface. What direction is the velocity? Acceleration? Net Force?

22. FBD Practice #2 A rock is raised upward by a string but is slowing. What direction is the velocity? Acceleration? Net Force?

23. FBD Practice #3 – The FBD below shows an object with a mass of 5 kg that is accelerating at 4 m/s/s. The force of tension acting on the object is ______ N. Hint: Find the net force first.

24. FBD Practice #4 – The FBD below shows an object with a mass of 20.Calculate the acceleration of the object.