Forces What is a Force? I- Any push or a pull. Like velocity and acceleration, a force is described...

Newton’s 1Newton’s 1stst Law of Law of Motion:Motion: States that an object at rest will remain at rest, an object in motion will remain in motion. Unless an outside force acts on it.

SectioSection 3n 3 Newton’s 1Newton’s 1stst and 2 and 2ndnd

LawsLaws

This tendency for an object to resist change is called InertiaInertia.

Depends on mass.Depends on mass.

More mass = more More mass = more inertia.inertia.

Newton’s 2Newton’s 2ndnd Law of Law of Motion:Motion: States that an object accelerates because a force acts on it.

Force

The stronger the force the greater the acceleration.

Big Force

The greater the mass of an object, the greater the force must be to accelerate the object.

Big MassBig

Force

Newton defined this in an equation F = ma.

ExampleExample:: How much force is needed to accelerate a sled 3m/s/s if the sled has a mass of 10kg?

Force = mass X acceleration. = 10 kg X 3m/s/s= 30kg/m/s/s or 30 N

N=N= NewtonNewton.. A Newton is the unit used to measure force. 1Newton is equal to 1kg/m/s/s

MomentumMomentum is the strength of an objects motion.

It depends on both the mass and velocity of an object.

Increase the mass or velocity of an object increases it’s momentum.

Newton’s Third Law of Newton’s Third Law of Motion:Motion: States that for every States that for every action there is an equal and action there is an equal and opposite reaction.opposite reaction.

Whenever one object applies a Whenever one object applies a force on another object, the force on another object, the second object applies a force of second object applies a force of equal strength on the first equal strength on the first

object.object.

Law of Conservation of Law of Conservation of Momentum:Momentum: the momentum of any the momentum of any object in a group can change, object in a group can change, but whatever but whatever momentum is lost by one object momentum is lost by one object must be gained by another.must be gained by another. The total momentum The total momentum remains the same, as long as no remains the same, as long as no outside force act on the group. outside force act on the group.

V.V.CircularCircular MotionMotion: : inward inward force that keeps objects force that keeps objects moving in a circle. Calledmoving in a circle. Called CentripetalCentripetal ForceForce

A.A. TorqueTorque causes objects to causes objects to rotate. rotate.

1.1. The more torque the faster The more torque the faster the object will spin. Torque the object will spin. Torque depends on two factors.depends on two factors.

2. The amount of force applied and the distance between the axis {imaginary line through

a rotating object}, and the point where the force is applied. AxisAxis

More More torquetorque

Less Less torquetorque

B- B- Astronomer Johannes Astronomer Johannes KeplerKepler discovered three discovered three Laws of Laws of Planetary MotionPlanetary Motion..

1- He realized that the planets did not orbit in a circle but in an ELLIPSE or squashed circles, this is 1st Law of Planetary Motion.

2- 2nd Law of Planetary Motion: Says planet

moves faster when they are closer to the sun and slower when they are farther away.

3- Period of Revolution: length of time it takes a planet to orbit the sun once.

3rd Law of Planetary Motion Says the larger the orbit the larger the period of revolution.

C- C- VelocitiesVelocities

1-1-Escape VelocityEscape Velocity = 37,000 km/hr the velocity needed to escape

the Earths gravitational pull.

2- 2- Orbital VelocityOrbital Velocity = 27,000 km/hr the velocity needed to orbit the Earth, without being pulled Earth.

VocabularyVocabulary::

1.1.ActionAction && ReactionReaction:: Forces on an object that are always equal in size and opposite in direction.

2.2.AxisAxis:: Imaginary line around which an object rotates.

3.3.BalancedBalanced:: Forces that cancel each other out.

5.5.EquilibriumEquilibrium:: When opposing forces on an object balance each other out the object is in a state of equilibrium.

6.6.Force:Force: Any push or pull that alters the velocity of an object.

7.7.Friction:Friction: Force that opposes motion.

4.4.CentripetalCentripetal forceforce:: Force that keep objects moving in a circle.

9.Law of conservation of momentum: The amount of momentum lost by one object in a group, is gained by another object in the group, the total amount of momentum remains the same.

8.Inertia: Tendency of an object to resist a change in motion, also Newton’s 1st Law.

11.2nd Law of motion: Objects accelerate because a force is applied to it.

10.1st Law of motion: An object at rest remains at rest an object in motion remains in motion unless an outside force acts on it.

13.Net force: Is zero if the object is balanced, or moving at a constant speed.

14.Momentum: Strength of an objects motion.

15.Torque: Strength of an objects rotation

12.3rd Law of motion: For every action there is an equal and opposite reaction

16. 16. GravityGravity:: force force that pulls object towards earth.

17. Microgravity: Condition in which gravity seems to disappear.

18. Terminal Velocity: is reached when air resistance = the weight of the object. Greatest velocity a falling Greatest velocity a falling object can reach.object can reach.

19. 19. PeriodPeriod ofof revolutionrevolution: : time it takes to go around the sun once.

20. 20. WeightWeight:: is the measure of the gravitational force on an objects mass.

21. TorqueTorque: the strength of an objects motion.

22. 22. FrictionFriction:: When two surfaces are in contact with each other.

23.23.Center of GravityCenter of Gravity:: Where gravity acts on an object.

24. 24. EscapeEscape VelocityVelocity:: velocity an object needs to reach to escape the earths gravitational pull.

25. 25. OrbitalOrbital VelocityVelocity:: the velocity an object needs to reach to orbit the earth.

26. 26. OrbitOrbit:: the path an object takes to orbit the sun or planet.

27. 27. EllipseEllipse:: Oval shape or squashed circle.

28. 28. ProjectileProjectile:: Anything hit, shot, hurled, or thrown forward, it moves downward and forward at the same rate.

29. 29. Kepler’sKepler’s LawsLaws:: 1st law = planets orbit in an ellipse. 2nd law = planet moves faster when they are closer to the sun and slower when they are farther away. 3rd law = the larger the orbit the larger the period of revolution.

30. 30. AirAir ResistanceResistance:: Fluid friction. Fluid friction.

31. 31. MomentumMomentum:: The strength of an object. The strength of an object.