1.What is a Force? Page #:_____ Paragraph #: ___ Page #:_____ Paragraph #: ___ Answer: Answer: Force is push or pull Force is push or pull Write an Example : Throwing a baseball Throwing a baseball36 2

2. The combination of all the forces acting on an object is called? Page #:_____ Paragraph #:___ Page #:_____ Paragraph #:___ Answer: Answer: The Net Force The Net Force 37 1

3. When 2 forces cancel each other out and they don’t change the object’s velocity, they are called? 3. When 2 forces cancel each other out and they don’t change the object’s velocity, they are called? Page #:____ Paragraph #:____ Page #:____ Paragraph #:____ Answer: Answer: Balanced Forces Balanced Forces 37 3

4. When the forces are Balanced, the net force is? Page #:______ Paragraph #:____ Answer: The net force is zero Object’s speed/velocity didn’t change 373

5. If the forces on an object are Unbalanced, the objects velocity changes.. Page #:_____ Paragraph #:___ Page #:_____ Paragraph #:___ T or F T or F Answer: Answer: True True 37 3

6. Which Italian scientist before Isaac Newton understood how forces work? Page #:____ Paragraph #:___ Page #:____ Paragraph #:___ Answer: Answer: Galileo Galilei Galileo Galilei 383

7. Describe in-full Newton’s First Law of Motion: Page #:______ Paragraph #:____ Page #:______ Paragraph #:____ Answer: Answer: If the net force on an object is zero, the object will remain at rest, or if it’s moving, it will continue moving in straight line at constant speed. If the net force on an object is zero, the object will remain at rest, or if it’s moving, it will continue moving in straight line at constant speed. 38 4

8. What is Friction? Page #:_____ Paragraph #:_____ Answer: T The force that brings nearly everything to a STOP!! RRRResists sliding between 2 objects 381

9. Give example of how Friction works. Page #:_____ Paragraph #:_____ Page #:_____ Paragraph #:_____ Answer: Answer: Friction will eventually bring your Friction will eventually bring your skateboard to a stop, unless you skateboard to a stop, unless youskateboard keep pushing on it… keep pushing on it… 38 1

10.What do the different types of Friction have in common? (Reading Check) Page #:____ Paragraph #:___ Page #:____ Paragraph #:___ Answer: Answer: The Frictional Forces always try The Frictional Forces always try to prevent one object from sliding to prevent one object from sliding on the other object. on the other object. 391

11. What causes Static Friction? Page #:_____ Paragraph #:___ Page #:_____ Paragraph #:___ Answer: Answer: It is caused by the attraction between the atoms on the two surfaces that are in contact. It is caused by the attraction between the atoms on the two surfaces that are in contact. The smoother the surfaces the less attraction between the atoms!! The smoother the surfaces the less attraction between the atoms!! 40 2

11. What causes Static Friction cont……. Static Friction prevents an object at rest from moving when a force is applied

12.Static Friction acts on an object at rest. Page #:_____ Paragraph #:_____ True or False Answer: T True 40 3

13. What does Sliding Friction do? Page #:____ Paragraph #:____ Page #:____ Paragraph #:____ Answer: Answer: Sliding friction slows Sliding friction slows down an object that down an object that slides slides 401

14. What causes Rolling Friction? Page #:_____ Paragraph #:_____ Page #:_____ Paragraph #:_____ Answer: Answer: Rolling friction occurs when Rolling friction occurs when an object rolls across a surface. an object rolls across a surface. Example: Example: Bicycle wheel rolling Bicycle wheel rolling on the ground on the ground a ground a ground 41 1

15. Which Frictional Force is stronger? Page #:______ Paragraph #:____ A. R olling Friction between wheels and ground B. Sliding Friction between box and ground Answer: B – Sliding Friction 41 2

Review questions 1. How would you describe a Force? Answer: Push or a Pull 2. What is Net Force? Answer: Combination of all the Forces 3. Describe what it means when forces are Balanced? Answer: The forces acting on the object are equal. Object does not move.

Review questions 4. W hat is the Net force when Forces are Balanced? Answer: Net force is “Zero” Object stays where it is!!!!!! Both boys are using same Force or pushing equally. The DOOR DOESN’T MOVE!!!!!!!

Review questions 5. W hat happens when Forces are Unbalanced? Answer: Unbalanced Forces are not equal and the object will move!!! The boy on the left is using greater force, therefore he is pushing the door toward the boy on the right!!!

Review questions 6. W hat are the 3 types of Friction or Frictional forces? Answer: Static friction Sliding friction Rolling friction

Review questions 7. How is Force measured? Answer: In a unit called Newton 8. What is a Newton? Answer: One Newton (symbol N NN N) is the force that will give an object whose is mass 1 kilogram an acceleration of 1 meter per second squared. N=1 kg·m/s²

9. In a tug of war, one student is pulling on a rope with a force of 10N and the other student with 8 N. What is the Net force on the rope? Or, the actual amount of force pulling on the rope? Answer: It is the difference between the stronger and the weaker force 1 0N – 8N = 2N

Review questions Study the diagram carefully and answer the questions 10. Are the Forces on the box Balanced or Unbalanced? Answer: Unbalanced 11. What is the Net Force on the box? Answer: 45N – 30 N = 15N N et force is 15N 45N30N WestEast

Review questions 12. In which direction did the box move? Answer: The box moved East 45N 30N West East