Presentation on theme: "Motion & Newton’s Laws Earth Systems. Definition and Formulas SPEED: a measurement of distance traveled in a given time. Speed = distance time Units:"— Presentation transcript:
Graphing If Sally got to school on foot and bus describe her movement according to the graph. 1: Sally at a slow constant speed walking to the busstop at 0.1 km/min 2: She stopped and sat waiting for the bus 0 km/min 3: She rode the bus at a faster constant speed of 0.25 km/min
Car A Car BCar C 1.Compare the motion of Car A an B. 2.Describe the motion of Car C.
ACCELERATION : Change in velocity Increase in velocity: acceleration Decrease in velocity: deceleration or negative acceleration. Acceleration: final velocity – initial velocity time Units: m sec 2
Acceleration equation rearranged for different variables Unknown: V i V i = V f - (a x t)
Acceleration “dot diagram” Dot represents an object’s position at different times. Acceleration: distance increases each second 1 sec 5 sec3 sec 7 sec5 sec3 sec Negative Acceleration / deceleration: distance decreases each second 7 sec
Video: Speed, Velocity, Acceleration, and Deceleration A Segment of: Basics of Physics: Exploring the Laws of MotionBasics of Physics: Exploring the Laws of Motion
Straight line versus curved line What is the speed traveled between 0-1sec? 10m/1s= 10 m/s What is the speed traveled between 4-5 sec? 10m/1s= 10 m/s CONSTANT SPEED What is the speed traveled between 0-1 sec? 2 m/1sec = 2 m/sec What is the speed traveled between 4-5 sec? 18 m/ 1 s = 18 m/sec CHANGING SPEED, ACCELERATION
Constant speed or acceleration? Constant speed Acceleration
A force is… a push or a pull. Friction, Drag, Gravity, and Weight are forces. Measured in unit Newton’s N = kg × m sec 2
Calvin explains Newton’s Laws Sir Isaac Newton is famous for explaining the motion of objects using mathematics.
1 st Law: The Law of Inertia An object in motion will stay in motion, An object at rest will stay at rest, unless an outside force acts on it. Newton’s 1 st Law rap http://www.youtube.com/watch?v=OaKc4PlrEY8 http://www.youtube.com/watch?v=OaKc4PlrEY8 Example: Table cloth trick Penny in a flask
1 st law stated again If no unbalanced force acts on an object the object will continue moving at the same speed in the same direction If an object is not moving and at rest the object will remain at rest until an outside force acts upon it.
Friction and gravity are the unbalanced forces that are acting on all the motion that we observe. Friction is the force that slows things down when two objects rub together. Friction slows objects until they stop, heats things up and wears them down. Gravity is the force pulling two objects together
Newton’s 1 st Law and You Don’t let this be you. Wear seat belts. Because of inertia, objects (including you) resist changes in their motion. When the car going 80 m/hour is stopped by the brick wall, your body keeps moving at 80 m/hour.
Inertia related to Mass Bigger masses have more… Smaller masses have less inertia.
Inertia = resistance to changes in motion. Large masses resist net forces and do not accelerate as easily as small masses. A large mass resists changing its velocity.
What if we put rockets on each creature? Large masses resist changing motion. Small masses change motion easily.
http://videos.howstuffworks.com/discov ery/29421-assignment-discovery- newtons-laws-of-motion-video.htm http://videos.howstuffworks.com/discov ery/29421-assignment-discovery- newtons-laws-of-motion-video.htm Assignment Discovery: Isaac Newton’s Principia Exploring the laws of motion: Newton’s 1st law Lego video: http://www.youtube.com/watch?v=NW E_aGqfUDs http://www.youtube.com/watch?v=NW E_aGqfUDs
2 nd Law Force = mass x acceleration Animations: \http://videos.howstuffworks.com/discovery/29421-assignment-discovery-newtons-laws-of- motion-video.htm http://www.youtube.com/watch?v=7_fbH-muvlw&feature=related “Three laws of motion” http://www.youtube.com/watch?v=7_fbH-muvlw&feature=related Assignment Discovery: Newton’s Laws of Motion (http://videos.howstuffworks.com/discovery/29421-assignment-discovery-newtons-laws-of-motion- video.htm) show for 2 nd lawhttp://videos.howstuffworks.com/discovery/29421-assignment-discovery-newtons-laws-of-motion- video.htm Force massacceleration
2 nd Law Newton = kg x m sec 2 One Newton is equal to the force required to accelerate one kilogram of mass at one meter/second every second.
2 nd Law (F = m x a) How much force is needed to accelerate a 1400 kilogram car 2 meters per second/per second? Write the formula F = m x a Fill in given numbers and units F = 1400 kg x 2 meters per second/second Solve for the unknown 2800 kg meters/second 2 or 2800 N
3 rd Law For every action, there is an equal and opposite reaction.
3 rd Law Whenever objects A and B interact with each other, they exert forces upon each other. When you sit in your chair, your body exerts a downward force on the chair The chair exerts an upward force on your body. ACTION REACTION
Newton’s 3rd Law in Nature Consider the propulsion of a fish through the water. action Reaction ACTION FORCE: A fish uses its fins to push water backwards. REACTION FORCE: the water reacts by pushing the fish forward
3 rd Law Flying gracefully through the air, birds depend on Newton’s third law of motion. As the birds push down on the air with their wings, the air pushes their wings up and gives them lift.
MOMENTUM Momentum = Mass x Velocity Law of conservation of momentum: If one object loses momentum, the other object gains momentum. Units of momentum: kg x m sec MassVelocity Momentum
Motion quiz Motion quiz followed by Newton’s Second Law penny lab
How could you increase the momentum of car E equal to the momentum of car A?
Gravity: force of attraction between all objects in the universe
Universal law of Gravitation F = G m 1 m 2 d 2 F : force of gravity G: constant of universal gravitation 6.67 x 10 -11 N ∙ m 2 kg 2 m 1 : mass of object one m 2 : mass of object two d 2 : distance between objects squared
F = G m 1 m 2 d 2 Use the universal law of gravitation to compare the force of gravity between 1. Earth & elephant 2. Earth & mouse 3. Elephant & mouse
Effect of mass and distance Gravitational force increases as mass increases Example: Gravitational force between elephant and Earth more then mouse and Earth. Gravitational force decreases as distance increases. Misconception: There is no force of gravity in outer space. Yes there is. But the amount of gravity depends on the 2 objects mass and the distance between the two objects.
Constant acceleration of free falling objects y = ½ g t 2 y = vertical distance traveled g = acceleration due to gravity (10m/s 2 ) (rounded from 9.8 m/sec 2) t = time
If a rock is falling off a canyon wall and falls for 20 seconds how far down has it fallen? y = ½ g t 2 Y= ½ x 10m/sec 2 x (20sec) 2 Y = ½ x 10m/sec 2 x 400 sec 2 Y = 2000 meters
Watch video http://videos.howstuffworks.com/science/falling- object-videos-playlist.htm#video-29420 http://videos.howstuffworks.com/science/falling- object-videos-playlist.htm#video-29420 http://videos.howstuffworks.com/science/gravity- videos-playlist.htm?page=2#video-29423 Issac Newton describing gravity and orbit http://videos.howstuffworks.com/science/gravity- videos-playlist.htm?page=2#video-29423 http://videos.howstuffworks.com/science/gravity- videos-playlist.htm?page=2#video-29600 2 nd explanation of Newton’s description of gravity http://videos.howstuffworks.com/science/gravity- videos-playlist.htm?page=2#video-29600 Feather vs hammer: http://www.youtube.com/watch?v=KDp1tiUsZw8&sa fety_mode=true&persist_safety_mode=1 vomit comet: http://www.youtube.com/watch?v=2V9h42yspbo
Acceleration due to gravity. Objects pick up speed at the same rate regardless of mass when gravity is the only force The force of gravity is greater on more massive objects but the inertia (resistance to motion) is greater too. For this reason a shot-put and softball will accelerate at the same rate. Acceleration due to gravity 10 m/sec 2 Light objects are affected by frictional forces more then heavy objects.
Terminal Velocity Falling objects will reach a maximum speed when the upward force of air resistance balances the downward force of gravity. For humans: 190 km/hr, 120 mi/hr http://www.youtube.com/watch?v=ur40 O6nQHsw&feature=related&safety_mo de=true&persist_safety_mode=1 Physics of sky diving 3 min http://www.youtube.com/watch?v=ur40 O6nQHsw&feature=related&safety_mo de=true&persist_safety_mode=1
Objects in orbit like the space shuttle The space shuttle is moving forward and in free fall toward the Earth. This results in a curving motion known as orbiting.
Not done 2012-2013 REACTION TIME ACTIVITY: 1.On a 7cm x 28cm poster board strip make a short line by one edge near the bottom of the strip label it 0
Calculate the distance an object will fall every.05 seconds Formula to use: y = ½ g t 2 y: distance g: acceleration due to gravity 10 m/sec2 In centimeters 1000 cm/sec 2 Time: calculate for.05 seconds.06 seconds.07 seconds Keep going until 0.22 seconds
1.Mark the falling distances that you have calculated along the edge of the poster board. Next to each mark write the falling time for which it was calculated. Be sure and measure from your zero mark each time. QUESTION: Why does the distance increase even though the time interval is the same?
QUESTION: why does the distance increase even though the time interval is the same? The falling object speeds up during each second it is falling – during each succeeding second the object is falling faster and therefore further than during each previous second.
Measure reaction times The person conducting the test holds the test strip by the top end. The testee holds his/her thumb and forefinger about 1 cm apart just below the zero mark. (Have the testee rest the catching arm on a table to ensure that he/she does not move the hand down to catch the strip. The tester lets go of the strip, and the testee snaps his/her fingers shut to catch it. Record 20 trials. Graph your learning curve as trial # vs. reaction time.