Presentation on theme: "MOTION: Describing and Measuring Motion"— Presentation transcript:
1 MOTION: Describing and Measuring Motion CHAPTER 10
2 Measuring Motion Motion is described as a change in position An object is considered in motion when observed in relation to a REFERENCE POINT.Describe motions with reference terms such as: north, south, east, west, up, down, right, left, etc.
3 Frame of ReferenceThe object or point from which movement is determinedAny object can appear to be in motion or at rest depending on the frame of reference of the observer.Motion can only be determined when there is a frame of referenceEarth is the most commonly used frame of reference
4 Frame of Reference and Relative Motion Relative Motion is based on the person describing the motion based on their frame of reference.Example: When you are standing on the ground, that is your frame of reference. Anything you see, watch, or measure will be compared to the reference point of the ground.
5 Frame of Reference Frame of reference for 2 girls… Red Dress Girl uses the moving vehicleAs her frame of reference and is notMovingYellow Dress girl uses her frame ofReference as a stationary position toSee the other girl in motion.Frame of Reference for theSkydiversPlane – in motion away from themThemselves – not in motionThe ground – in motion towards them
6 Example 1: Sitting at your desk, how fast are you moving? Relative to the ground: ZERORelative to the sun: 2.97 X104 m/s! An observer standing on the sun would say you are moving at 2.97 X104 m/s
7 Example 2:While sitting at a red light a bus stops in the lane next to you…as you are daydreaming looking at the side of the bus…you all of a sudden feel like you are rolling backwardsThen you realize it is the bus moving forwards when you take into account a stationary frame of reference.This is your brain “confused”
8 Did you know?Motion Sickness is caused by your brain getting two different sets of information about your body’s motion based on its frame of reference, the information from your eyes and the information from your inner earTo help with motion sickness, try to look forward at a point far in the distance and stay focused on that.
9 Distance vs. Displacement Vector (amount and direction)Direction DOES matter!The path does NOT matter!The straight-line distance (and direction) the object has travelled from its starting point.In the Daytona 500, the cars experience zero displacement (they start where they end).Scalar (amount only)Direction does NOT matter.The actual path matters!The total distance traveled.In the Daytona 500, the cars travel a distance of 500 miles.
10 Distance vs. Displacement What is the overall distance traveled in the picture below?What is the overall displacement in the picture below?Leg 1 Distance = ______Leg 1 Displacement = _____Leg 2 Distance = ______Leg 2 Displacement = _____Leg 3 Distance = ______Leg 3 Displacement = _____Final Distance = ______Final Displacement = _____Leg 2Leg 1STARTLeg 3End
12 Vector DiagramsThe objects motion is represented with an arrow in the direction traveling.The size of the arrow indicates the relative speed of that object.
13 Practice with Frames of Reference / Distance and Displacement Worksheet as a classfun with mapping … check out Santa’s route to your house!
14 A little lesson through music Speed and VelocityA little lesson through music
15 SPEED SPEED – the rate of change in position or rate of motion INSTANTANEOUS SPEED – Rate of motion at any given instant(ex: speedometer in a car)CONSTANT SPEED – A speed that does not vary(ex: cruise control)Usain Bolt races at ESPN video clipUsain Bolt Olympics
16 Constant Speed vs. Instantaneous Speed….Let’s graph
17 CALCULATING SPEEDWhen we calculate speed, we are calculating the average speed traveled.AVERAGE SPEED – a measure of total distance traveled divided by total time of travelSPEED (v) = DISTANCE (d)TIME (t)UNITS FOR SPEED ---- m/s
18 DISTANCE-TIME GRAPHThe distance covered by an object is noted at regular intervals of time.
19 Measuring Speed Sport Science - John Wall Sport Science - Lebron James Sport Science - Ndamukong Suh
20 VELOCITY VELOCITY – Describes both speed AND direction. Velocity can change even if the speed of the object does not change.Calculating Velocity:Velocity = Displacement / timeAnswers will include direction
21 Velocity – Time GraphA velocity – time graph can show acceleration.
22 Distance-Time Graph vs. Velocity Time Graph Shows velocity of object, time.Can calculate AccelerationShows Motion, distance traveled, and time.Can calculate speed.
23 ACCELERATION ACCELERATION – The rate of change of velocity. Acceleration can be a change in speed OR directionCircular motion is a constant accelerationExample: blades of a fan
27 CALCULATING ACCELERATION Divide the change in velocity by the time intervalAcceleration (a) = (final velocity – initial velocity)time intervala = (vf – vi)t* Unit for Acceleration: m/s2 (plus direction)
28 Acceleration Practice Natalie accelerates her skateboard along a straight path from 0 m/s to 4.0 m/s in 2.5 seconds. Find her average acceleration.a = m/s – 0 m/s2.5 sa = 1.6 m/s2 along her path* Practice: p. 328 # 2-5
29 Example: Positive Acceleration Acceleration = (30 m/s – 0 m/s)/10 sa = 3 m/s/sThe car’s acceleration is increasing 3 m/s2
30 Examples: Negative Acceleration a = (0m/s – 20 m/s)/10 sa = - 2 m/s/sThe cars acceleration is decreasing at 2 m/s2
31 MOTION AND FORCE FORCE – A push or a pull one object puts on another. BALANCED FORCE – Forces that are equal in size and opposite in direction.UNBALANCED FORCE (NET FORCE) – Forces that are unequal in size…Cause a change in motion.Unbalanced forces always change the velocity of the object.
32 Balanced vs. Unbalanced Forces Balanced force pushing on each otherBalanced Force opposite in direction - pullingUnbalanced forces….showing displacement of the objectUnblalanced Forces – adding up to displace the object in one direction
34 Forces that Act on Objects 1. Normal Force – A support force when one object is in contact with a stable object (ex: Book on a table)2. Tension Force – A force transmitted through a string, rope, or cable3. Gravitational Force – The force of attraction to a very large object in the universe4. Friction Force – The force that opposes motion between two surfaces.
38 FRICTIONFRICTION – The force that opposes motion between two surfaces that are touching each other.2 TYPES OF FRICTION:STATIC FRICTION – The friction between surfaces that are stationary.KINETIC FRICTION – The friction between moving surfaces.Kinetic Friction can be SLIDING or ROLLING
39 Increasing or Decreasing Friction Increase Friction by using rough surfacesEX: Cleaning surfaces with a rough spongeDecrease Friction by adding a liquidEx: Oil, WD40