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Ch. 2 sec.1-force of nature

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I hope to study and complete all your notes from this presentation to remember all what did we say in the class. Good Luck.

I hope to study and complete all your notes from this presentation to remember all what did we say in the class. Good Luck.

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• 1. Forces of Nature Gravitational Magnetic
• 2. The Nature of Force
• What is a Force?
• A force is a push or a pull.
• Like velocity and acceleration, a force is described by its strength and the direction in which it acts.
• The strength of a force is measured by Newton (N).
• 3. Net force (Combining force); It is the total amount of Force, ( minus the forces that cancel each other out ). Force of gravity Force of muscles Net force
• 4. Balanced Forces Unbalanced Forces When the net force is Zero. -> NO movement When the net force is NOT Zero. -> movement
• 5. 2 Kg ?
• Static Equilibrium Balanced forces
• When all forces are balanced.
• The net force is Zero.
• There is NO movement.
3 Kg
• 6. 50 N 100 N 100 N 50 N 50 N 50 N
• 7. Balanced or unbalanced? Action Reaction Gravity Inertia Friction
• 8. Gravity balanced UN Time (mSec) Speed (m/s) BALL Ground
• 9. Inertia balanced UN Time (mSec) Speed (m/s) BALL PUTTER
• 10. Friction balanced UN Time (Sec) Speed (m/s) SKATE
• 11.
• Friction results from relative motion between objects.
• Frictional forces are forces that resist or oppose motion.
2.2 Friction
• 12.
• Static friction
• {A friction that acts on objects that are not moving}.
• Sliding friction
• { A friction that occurs when two solid surfaces slide above each other}.
• Rolling friction
• {A friction that occurs when an object rolls across a surface.
2.2 Types of Friction
• 13. 2.2 Types of Friction
• Air friction
• { A friction that occurs when a solid object moves through the air}.
• Fluid friction
• { A friction that occurs when a solid object moves through a fluid}.
• 14. Gravity The Apple & the Moon
• Isaac Newton realized that the motion of a falling apple and the motion of the Moon were both actually the same motion , caused by the same force - the gravitational force .
• Gravity is a force that pulls objects toward each other.
• 15. Universal Gravitation
• Newton’s idea was that gravity was a universal force acting between any two objects .
• Factors Affecting Gravity;
• Mass : is a measure of
• the amount of matter in an
• object.
• Distance : it is
• between two objects.
• The farther apart two objects are,
• the lesser gravitational forces
• Between them.
• 16. At the Earth’s Surface
• Newton knew that the gravitational force on the apple equals the apple’s weight , mg , where g = 9.8 m/ s 2 .
• Gravitational force
• INCREASES with Mass
• DECREASES with Distance
W = mg
• 17. Gravity and Motion Free Fall Free fall- when gravity is the only force acting on an object (free fall acceleration is directed toward center of earth) The acceleration of gravity ( g ) for objects in free fall at the earth's surface is 9.8 m/s 2 . Galileo found that all things fall at the same rate in the absence of air resistance, regardless of their mass
• 18. Air Resistance
• In air…
• A stone falls faster than a feather
• Air resistance affects stone less
• In a vacuum
• A stone and a feather will fall at the same speed.
• Terminal Velocity : it is reached when the force of air resistance equals the weight of the object
• 19. Projectile Motion When an object is thrown into the air, two forces and two motions affect the movement of the object. The object may be thrown horizontally with a certain force, but the vertical force of gravity combines to affect the motion. Slow projectile - shoot a monkey Fast projectile - shoot a monkey
• 20. Projectile Motion seconds 0 2 1 3 Velocity (m/s) forward downward 0 50 9.8 19.6 29.4 39.2
• 21. Projectile Motion seconds 0 2 1 3 Velocity (m/s) forward downward 0 50 9.8 19.6 29.4 39.2 49 48 47 46
• 22.