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.