2Forces Force is a push or pull on an object. Unit for force: N or Newton.
3Balanced forces Where there are two forces that counteract each other and result in no movement (EQUAL)Unbalanced forcesOne force is greater than the other force.(UNEQUAL)
4Friction A force that resists motion and can cause heat Lubricants help reduce frictionTypes of frictionSlidingRollingFluidStatic
5Types of friction Static acts on objects that are not moving Always acts in opposite direction to applied forceSlidingOpposes direction of motion as an object slidesLess then static frictionRollingFriction that acts on rolling objects100 to 1000 times less than static and sliding frictionFluidOpposes the motion of an object through a fluidFluids include gases and liquidsAir resistance – fluid friction acting on an object movingthrough the air
6Newton’s Laws of Motion 1st Law: Objects at rest remain at rest, or objects in motion remain in motion unless acted upon by a force. (unbalanced)2nd Law: The acceleration of a body depends on the ratio of the acting force to the mass of the body. (unbalanced)F = m x a3rd Law: for every action there is an equal and opposite reaction. (balanced)
71st Law of Motion (Law of Inertia) Inertia: force that is resistant to the direction of the motionThe forces are UnbalancedExamples: Inertia belts (seat belts)
82nd Law of Motion Concept: Acceleration The forces are unbalancedExamples: hitting a golf ball gently vs. hard.F = maAnswer = _50__ newtons
9Problem 1How much force is needed to accelerate a500.0 kg car at a rate of m/s/s?
10Problem 2A 100 N force causes an object to accelerate at2 m/s/s. What is the mass of the object?
11Problem 3A 1.5 kg ball is kicked with a force of 450 N.What acceleration did the ball receive?
123rd Law of Motion Action/ Reaction Concept: Action/Reaction of objectsForces are balancedExamples: Stationary objects, rockets being launched
13Laws of motion Interactives interactives/newtons-laws-of-motion- interactive.htm
14Motion of a falling object after being ProjectileMotionMotion of a falling object after beinggiven an initial forward velocityCombination of initial vertical forceand downward force of gravityCauses object to follow a curved path
15Gravity and Free Falling Objects Gravity: The attraction between two objects.All objects fall at a rate of 9.8 m/s2Gravity acts between two massesAll masses exert the force of gravity – universal forceGalileo did an experiment at the leaning tower of Pisa in Italy with bowling balls. Both balls fell at the same rate.
16Air ResistanceForce that slows down falling objects due to the atmosphere and surface area of the object.
17Newton’s Law of Universal Gravitation Shows that objects are attracted to one another in proportion to their masses and their distances away from the object.
18Feather vs. RockEarth: feather would float down (air resistance) while the rock would drop at 9.8 m/s/sMoon: feather and rock would drop at same rate due to no atmosphere and air resistance.
19Both fall at the same rate due to there being no air. What about a vacuum?vac·u·um [ vákyoo əm ]space empty of matter: a space completely empty of matter but not achievable in practice on Earthspace with all gas removed: a space from which all air or gas has been extractedemptiness caused by absence: an emptiness caused by somebody or something's absence or removalBoth fall at the same rate due to there being no air.
20Gravity and Weight Gravi ty Mass – measure of amount of inertia Weight – force of gravity pulling on an objectWeight is product of mass and acceleration due to gravity ( 9.8 m/s/s)W = mgW- weight in newtonsm- mass in kilogramsg- acceleration due to gravity in meters per second squared