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Forces and Motion ppt pdf.pdf
- 1. Section 1 Gravity and Motion Section 2 Newton’s Laws of Motion Section 3 Momentum
- 2. • Gravity and Acceleration Objects fall to the ground at the same rate because the acceleration due to gravity is the same for all objects. • Acceleration Due to Gravity The object’s downward velocity increases by 9.8 m/s. Gravity and Falling Objects Iron ball Wood ball
- 3. Acceleration of gravity is independent of the mass of the falling object!
- 4. • Velocity of Falling Objects You can calculate the change in velocity with the following equation: ¨ ∆v = g X t • If an object starts at rest, this equation yields the velocity of the object after a certain time period.
- 6. • Air resistance is the force that opposes the motion of objects through air. • The amount of air resistance acting on an object depends on the size, shape, and speed of the object. Air Resistance and Falling Objects
- 8. ¨ As the speed of a falling object increases, air resistance increases. ¨ The upward force of air resistance continues to increase until it is equal to the downward force of gravity. The object then falls at a constant velocity called the terminal velocity.
- 9. ¨ An object is in free fall : - When There Is No Air Resistance - only if gravity is pulling it down and no other forces are acting on it. A vacuum is a place in which there is no matter. Objects falling in a vacuum are in free fall because there is no air resistance.
- 10. ¨ Astronauts Ìýfloat Ìýin Ìýorbiting Ìýspacecrafts Ìý because Ìýof Ìýfree Ìýfall.
- 11. ¨ Orbiting and Centripetal Force The unbalanced force that causes objects to move in a circular path is called a centripetal force. Gravity provides the centripetal force that keeps objects in orbit. Too slow => Object falls back down to Earth Too fast => Object escapes Earth’s gravity
- 12. ¨ Projectile Ìýmotion Ìýis Ìýthe Ìýcurved Ìýpath Ìýan Ìýobject Ìý follows Ìýwhen Ìýit Ìýis Ìýthrown Ìýor Ìýpropelled Ìýnear Ìýthe Ìý surface Ìýof Ìýthe ÌýEarth. ¨ Projectile Ìýmotion Ìýhas Ìýtwo Ìýcomponents Ìýthat Ìýare Ìý independent Ìýof Ìýeach Ìýother;; - horizontal Ìývelocity - vertical Ìývelocity Ìý
- 14. 1.A body continues at rest or in uniform motion in a straight line unless acted upon by some net force. An astronaut floating in space will continue to float forever in a straight line unless some external force is accelerating him/her.
- 15. ¨ Friction Ìýbetween Ìýan Ìýobject Ìýand Ìýthe Ìý surface Ìýit Ìýis Ìýmoving Ìýover Ìýis Ìýan Ìýexample Ìýof Ìý an Ìýunbalanced Ìýforce Ìýthat Ìýstops Ìý motion. Ìý
- 16. ¨ Inertia is the tendency of all objects to resist any change in motion. ¨ Mass is a measure of inertia. - Small mass has less inertia - Large mass has greater inertia Newton’s first law is sometimes called the law of inertia.
- 17. ¨ The acceleration of an object depends on the mass of the object and the amount of force applied a = F/m ó F = m a
- 18. ¨ Part 1: Acceleration Depends on Mass The acceleration of an object decreases as its mass increases. ¨ Part 2: Acceleration Depends on Force An object’s acceleration increases as the force on the object increases. ¨ The acceleration of an object is always in the same direction as the force applied.
- 21. ¨ Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first. To every action, there is an equal and opposite reaction. All forces act in pairs.
- 22. ¨ Force ÌýPairs ÌýDo ÌýNot ÌýAct Ìýon Ìýthe ÌýSame ÌýObject. ¨ When Ìýa Ìýforce Ìýis Ìýexerted, Ìýthere Ìýis Ìýalways Ìýa Ìý reaction Ìýforce. A Ìýforce Ìýis Ìýalways Ìýexerted Ìýby Ìýone Ìýobject Ìýon Ìý another Ìýobject. Ìý
- 23. • The momentum of an object depends on the object’s mass and velocity. P Ìý= m x v
- 24. ¨ The law of conservation of momentum states; - that any time objects collide, the total amount of momentum stays the same. - After two objects stick together, they move as one object - The combined objects have a different velocity because momentum is conserved and depends on mass and velocity. • So, when the mass changes, the velocity must change, too.
- 26. Objects Bouncing Off Each Other • When two objects bounce off each other, momentum is transferred from one object to the other. • The transfer of momentum causes the objects to move in different directions at different speeds.
- 27. ¨ Because action and reaction forces are equal and opposite, momentum is neither gained or lost in a collision