6 Acceleration What is Motion? The rate of change in velocity Positive acceleration = speeding upNegative acceleration = slowing down (decelerate)Acceleration = Vfinal – VinitialTimeor = ∆Velocity
7 Motion Questions ) What units are used to measure speed? ) What units are used to measure acceleration?) What is another way to say “slowing down” in terms of acceleration?
8 Answer this in the “In” for Forces Name 3 forces off the top of your head.
9 What is a Force?FORCE = Any push or pull which causes something to move or change its speed or direction
10 What is a Force?Forces can be BALANCED or UNBALANCEDBalanced forces are equal in size and opposite in directionArrow thickness is equal.Net Force = 0.Balanced forces result in no movement.
11 What is a Force? Unbalanced forces in the same direction Net Force = Forces can be BALANCED or UNBALANCEDUnbalanced forces in the same directionArrow thickness is not equal.Net Force =When two forces act in the same direction, the net force is the sum of the two individual forces. Box moves right
12 What is a Force?Forces can be BALANCED or UNBALANCEDUnbalanced forces are not equal in size and/or opposite in direction. If the forces on an object are UNBALANCED, we say a NET force results.Net force =Box moves right.
14 “Out” Force Questions) What famous physicist are units of force named after?2) If Moby has a mass of 50 kg and Tim has a mass of 40 kg, who would require more force to move?
15 Gravity and FrictionNew Cornell notes (in, out, through) for gravity and friction.
16 In For Gravity and Friction Does a person have gravity?
17 What is Gravity? GRAVITY: An attraction force between all masses Newton’s universal law of gravitation: Every object in the universe exerts a gravitational attraction to all other objects in the universeThe amount of gravitational force depends upon the mass of the objects and the distance between the objects
18 What is Gravity? The greater the mass, the greater the force The greater the distance, the less the forceAcceleration due to gravity = 9.8 m/s/s or 9.8 m/s2
19 What is Weight?Weight is a measure of the gravitational force between two objectsThe greater the mass the greater the force (weight)Measured in units called Newtons (N)In the standard system units are pounds (lbs)
20 “Out” Gravity Questions ) How does the gravity on the moon compare to the gravity on Earth?) Why don’t you notice your own gravitational pull on the Earth?) On what two things does the force of gravity depend?
21 What is Friction? Friction = A force that opposes or slows down motion Caused by the physical contact between moving surfacesThe amount of friction depends upon 2 things: 1.) kinds of surfaces and 2.) force pressing the surfaces togetherChanges motion into heat
22 What is Friction? 4 Types of Friction: Rolling Friction (bike tire on the road)Sliding Friction (book sliding on table)Fluid Friction (object moving through air or water)Static Friction (force holding things still)
23 Air resistance: The force of air exerted on a falling object The air pushes up as gravity pulls downDependent upon the shape and surface area of the objectWhen the air resistance equals the force of gravity, terminal velocity is reachedTerminal velocity is the highest velocity that an object will reach as it falls
24 The feather reaches terminal velocity quickly The feather reaches terminal velocity quickly. Air resistance and gravity cancel each other out so the feather stops accelerating. The elephant keeps accelerating due to its shape, surface area and mass.
25 An Elephant and a Feather both fall at the same rate when air is removed (vacuum). Apollo astronauts dropped a feather and a hammer during their lunar experiments. Both landed at the same time.
26 Examples of Friction?What are some ways athletes use friction?
29 Newton's Laws of MotionFirst Law: An object at rest stays at rest or an object in motion, stays in motion (in the same direction/at the same speed) unless acted upon by an unbalanced forceAlso called the law of inertia
30 Inertia is: A property of matter The tendency of an object to resist any change in its motionThe greater the mass the greater the inertiaThe greater the speed the greater the inertia
31 Examples of Newton’s 1st Law a) car suddenly stops and you strain against the seat beltb) when riding a horse, the horse suddenly stops and you fly over its headc) the magician pulls the tablecloth out from under a table full of dishesd) the difficulty of pushing a dead carf) car turns left and you appear to slide to the right
33 Newton's Laws of MotionSecond law: The greater the force applied to an object, the more the object will accelerate. It takes more force to accelerate an object with a lot of mass than to accelerate something with very little mass.The player in black had more acceleration thus he hit with a greater amount of force
34 Newton's Laws of Motion Second law: The greater the force, the greater the accelerationThe greater the mass, the greater the force needed for the same accelerationCalculated by: F = ma(F = force, m = mass, a = acceleration)
35 Examples of Newton’s 2nd Law a) hitting a baseball, the harder the hit, the faster the ball goesb) accelerating or decelerating a carc) The positioning of football players - massive players on the line with lighter (faster to accelerate) players in the backfieldd) a loaded versus an unloaded truck
36 Examples of Newton’s 2nd Law The second law states that unbalanced forces cause objects to accelerate with an acceleration which is directly proportional to the net force and inversely proportional to the mass. This one is telling us that big heavy objects don’t move as fast or as easily as smaller lighter objects. It takes more to slow down a charging bull then to slow down a charging mouse.
37 Newton's Laws of Motion “In” Activity How can climbing into a boat from a dock be used to explain Newton’s 3rd Law?
38 Newton's Laws of Motionthird law: For every action force, there is an equal and opposite reaction force. (Forces are always paired)
43 Momentum: The quantity of motion A property of moving objectsCalculated by: P = mv(p = momentum, m = mass, v = velocity)Calculating MomentumMomentum Practice
44 Momentum: The quantity of motion Law of conservation of momentum: the total amount of momentum of a group of objects does not change unless outside forces act on the objectsThis is an Inelastic collision. Notice how there is no bounce.The Diesel engine’s momentum before the collision is _________The Diesel engine + the flat car momentum after the collision is _________.No momentum was lost or gained.
45 Newton’s Laws Out Activity ) Why does a ball roll across a rug and come to a stop?) What is a net force?) Give an example of Newton’s 3rd Law: