Chapter 11: Force and Newton’s Laws

1. Chapter 11: Force and Newton’s Laws Mr. Polard Sixth Grade Physical Science

2. Section 1 – Newton’s First Law

3. Section 1 – Vocabulary • Force: a push or a pull (p. 310) • Net Force: combination of all forces acting on an object (p. 311) • Balanced Forces: two or more forces whose effects cancel each other out and do not change the motion of an object (p. 311) • Unbalanced Forces: two or more forces acting on an object that do not cancel, and cause the object to accelerate (p. 311) • Newton’s First Law of Motion: states the if the net force acting on an object is zero, the object will remain at rest or move in a straight line with a constant speed (p. 312) • Friction: force that acts to oppose sliding between two surfaces that are touching (p. 312)

4. Section 1 - Notes • _____Force______________________ - Push or Pull on an Object • The combination of all the forces acting on an object is the ______net______ force. • When forces are ___balanced____ forces, they cancel each other out and do not change an object’s motion; when forces are _____unbalanced______forces, the motion of an object changes. • Newton’s ____first law_____ of motion - an object will remain at rest or move with constant speed unless a net force is applied • ____Friction___________is a force that resists sliding between two touching surfaces or through air or water. • Friction ____slows down______ an object’s motion. • ___Static_______friction – the type of friction that prevents an object from moving when a force is applied • ____Sliding______ friction is due to the microscopic roughness of two surfaces; it slows down a sliding object. • ____Rolling____ friction between the ground and a wheel allows a wheel to roll.

5. Section 2 – Newton’s Second Law

6. Section 2 – Vocabulary • Newton’s Second Law of Motion: states that an object acted upon by a net force will accelerate in the direction of the force, and that the acceleration equals the net force divided by the object’s mass (p. 316) • Weight: a measurement of force that depends on gravity; measured in newtons(pp. 53, 317) • Center of Mass: point in an object that moves as if all of the object’s mass were concentrated at that point (p. 322)

7. Section 2 - Notes • Newton’s ____second law____ of motion connects force, acceleration, and mass; it explains that an object acted upon by a force will accelerate in the direction of the force; acceleration equals net force divided by mass. • ___Gravity_______- attractive force between two objects; depends on the mass of the objects and distance between them; gravitational force is also called ____ weight_____. • The second law explains how to ___calculate_____ the acceleration of an object if its mass and the forces acting on it are both known. • In circular motion, the _____centripetal______ force is always perpendicular to the motion. • The ___terminal velocity_____is reached when the force of gravity is balanced by air resistance; the size of the air resistance force depends on the shape of an object and its speed. • An object can speed up, slow down, or turn in the direction of the net force when ___unblanced______ forces act on it.

8. Section 3 – Newton’s Third Law

9. Section 3 – Vocabulary • Newton’s Third Law of Motion: states that forces always act in equal but opposite pairs (p. 323)

10. Section 3 - Notes • Newton’s ______third law________ of motion states that forces always act in equal but opposite pairs; for every action there is an equal and opposite reaction. • Action – reaction forces are always the same size but are in ____opposite_______ directions and act on different objects. • When the mass of one object is considerably ____larger________ than the mass of another object, the action-reaction force is not noticeable. • ____Air______ and ______Water_____ exert action-reaction forces with objects such as hands or canoe paddles • A ______rocket______ launches due to the equal but opposite forces of the burning fuel.