1. Chapter 10

2. Section 1 – The Nature of Force
Force - a push or pull
Like velocity and acceleration, a force is described by its strength and by the direction in which it acts.
SI unit Newton
The combination of all forces acting on an object is called the net force.
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3. Section 1 – The Nature of Force
Unbalanced Forces - acting on an object will change the object’s motion
Unbalanced forces acting on an object result in a net force and cause a change in the object’s motion.
Equal forces acting on one object in opposite directions are called balanced forces.
Balanced Forces - acting on an object will not change the object’s motion
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4. Section 2 – Friction and Gravity
Friction - The force that two surfaces exerts on each other when they rub against each other.
The strength of the force of friction depends on two factors: how hard the surfaces push together and the types of surfaces involved.
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5. Section 2 – Friction (cont.)
Types of friction
Static Friction – Friction that acts on objects that are not moving
sliding friction - objects slide against each other
rolling friction - object is round or has wheels
fluid friction - object moves through fluid (swimming)
Is friction bad?
ice, walking, car, bike
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6. Section 2 – Gravity The force that pulls objects toward Earth
Law of Universal Gravitation - The force of gravity acts between all objects in the universe.
Too factors affect the gravitational attraction between objects: mass and distance.
Mass - measure of the amount of matter in an object
Inverse relationship between distance between object and their gravitaional pull
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7. Section 2 – Gravity (cont.)
Weight - measure of the force of gravity on an object
Earth vs. Moon
Weight (Newtons) = mass x 9.8m/sec2
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8. Section 2 - Gravity (cont.)
Free fall - only gravity acting on the object (in a vacuum)
In free fall, the force of gravity is an unbalnced force, which causes an object to accelerate.
Acceleration due to Gravity = 9.8 m/s2
Air Resistance - Objects falling through the air experience a type of fluid friction
Terminal velocity – The greatest velocity a falling object reaches
air resistance forces balanced with gravity

9. Section 2 – Gravity (cont.)
Projectile – An object that is thrown
Projectile motion –throw object horizontally (football, soccer)
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10. Section 3 – Newton’s First & Second Laws
Newton’s First Law of Motion
An object at rest will remain at rest, and an object that is moving at a constant velocity will continue moving at constant velocity, unless it is acted upon by an unbalanced force.
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11. Section 3 – Newton’s First Law
Inertia - the tendency of an object to resist a change in it’s motion
Direct relationship between mass and inertia. (One can say that mass is a measure of an objects inertia.)
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12. Section 3 – Newton’s Second Law
Newton’s Second Law of Motion
The acceleration of an object is directly proportional to force and inversely proportional to mass.
Acceleration = Net Force/Mass
Force = Mass x Acceleration F=ma
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13. Section 3 – Newton’s Second Law
Mass - the amount of matter in an object (SI units = kilogram (kg))
Force = Newtons (N), Mass=kilograms (kg), Acceleration = m/sec2
Sample Problems pg.351
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14. Section 4 – Newton’s Third Law (cont.)
Newton’s Third Law of Motion
If one object exerts a force on another object, then the second object exerts a force of equal strength in the opposite direction on the first object.
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15. Section 4 – Newton’s Third Law (cont.)
Action-Reaction – pg. 354 Gymnast, kayaker, dog (Squid, skater, kick, walking)
Action Reaction Pairs
Motion?
Forces cancel? Volleyball pg.355
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16. Section 4 – Momentum
Newton called momentum an objects quantity of motion
The momentum of a moving object can be determined by multiplying the object’s mass and velocity.
Momentum = mass x velocity
Sample problems pg.356
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17. Section 4 – Momentum (cont.)
Law of Conservation of Momentum
The total momentum of any group of objects remains the same (is conserved), unless outside forces act on the objects.
Train examples - overheads pg.358
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18. Section 5 – Orbiting Satellites
Rocket lift off - Newton’s third law - gasses expelled with a downward force, exert an equal but opposite force upward on the rocket.
Satellite - any object that orbits another object in space
centripetal force - any force that causes an object to move in a circular path
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19. Section 5 – Orbiting Satellites (cont.)
satellites in orbit around the Earth continually fall toward Earth, but because Earth is curved they travel around it pg.364
Satellite Motion
Satellite location – LEO, Geo Synchronous
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20. Chapter 10 Vocabulary gravity force Mass net force Weight inertia
Free fall
Air resistance
Terminal velocity
Projectile
momentum
conservation of momentum
satellite
centripetal force
force
net force
inertia
Newton’s first law
Newton’s second law
Newton’s third law
Friction
Static Friction
Sliding Friction
Rolling Friction
Fluid Friction
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