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PATTERNS OF MOTION AND EQUILIBRIUM

PATTERNS OF MOTION AND EQUILIBRIUM. Galileo`s concept of inertia. Force: is a push or pull. It is needed to start an object moving. No force is needed when it starts moving, just the force to overcome friction.

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PATTERNS OF MOTION AND EQUILIBRIUM

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  1. PATTERNS OF MOTION AND EQUILIBRIUM

  2. Galileo`s concept of inertia • Force: is a push or pull. It is needed to start an object moving. No force is needed when it starts moving, just the force to overcome friction. • Inertia: the property of things to resist changes in motion. So a ball moving horizontally would move forever if friction is totally absent.

  3. Concept of inertia

  4. Concept of inertia • Every material object possesses inertia: how much depends on its amount of matter. The much matter, the much inertia (that means it has more mass) • When comparing 2 objects, you should compare the abilities to be resistant to a change in motion.

  5. Mass vs Weight • Mass: quatity of matter in an object. It`s a measure of inertia that an object exhibits in response to any effort made to start it, stop it, or change its state of motion in any way. (SI Unit: Kilogram) • Weight: force upon an object due to gravity. (SI Unit: Newton) W=m x g • Directly proportional to each other. • Gravitation force: 9.8N • 1 Kg= 9.8N

  6. Vectors and scalars • Vector quantity: directed quantity. It has to be specified not only by magnitude (size) but by direction as well. May be represented by arrows Ex: velocity • Scalar quantity: can be specified by magnitude alone. Ex: speed

  7. Adding vectors • Vectors that are add together are called component vectors. The sum of component vectors are called a resultant. • DO NOT MIX VECTORS!!!!!

  8. Net force • Objects don`t speed up, slow down or change direction unless a force acts. • The NET FORCE is the total force acting on an object. A combination of forces that changes an object`s state of motion. • It is a vector quantity, arrows represented the direction of the quantity.

  9. The equilibrium rule • Forces are balanced • There`s no motion • Called mechanical equilibrium

  10. Support force • Called NORMAL force • The force that supports an object against gravity

  11. Dynamic equilibrium • STATIC equilibrium: when an object is NOT moving • DYNAMIC equilibrium: once in motion, if there is no net force to change the state of motion, it moves at an unchanging speed. ∑F= 0

  12. Force of friction • Resistive force that opposes the motion or attempted motion of an object past another with which it is in contact. • For solids, liquids and gases • ALWAYS in opposite direction to motion • Ex: air resistance

  13. Force of friction • Depends on: the kind of material and how much surfaces are pressed together

  14. Types of Friction • Dry friction: • Static friction: the object has no motion. • Sliding friction: the object moves. • Lubricated friction: Needs a lubricant to start moving. • Fluid friction: resistance in liquids. • Air resistance: resistance of an object to move in the air.

  15. Instantaneous speed • The speed at any instant • Most of the time, it is different than the average speed

  16. Velocity • Constant velocity means constant speed and direction • Direction in a straight line: no curves • No change in velocity, means no acceleration • Works with displacement (net distance)

  17. Motion is relative • Everything is always moving • Motion is relative to different objects

  18. Acceleration • Variation is motion, in velocity

  19. Average acceleration

  20. Acceleration • Recognizing Acceleration on a Graph Acceleration can be shown on a graph of velocity versus time.

  21. Tracks • Circular Motion: Continuous Acceleration An object traveling in a circular motion is always changing its direction. Therefore, its velocity is always changing, so it is accelerating. • The acceleration that occurs in circular motion is known as centripetal acceleration.

  22. Tracks • Linear motion: motion along a straight line. • It can be uniform, with constant speed or non uniform with a variable speed • An example of linear motion is that of a ball thrown straight up and falling back straight down. • objects not subjected to forces will continue to move uniformly in a straight line indefinitely

  23. Tracks • Parabolic motion: A projectile is an object upon which the only force is gravity. Gravity, being a downward force, causes a projectile to accelerate in the downward direction.

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