1 / 62

LINEAR MOTION

LINEAR MOTION. Chapter 2. Motion . Everywhere – people, cars, stars, cells, electricity, electrons Rate = Quantity/time How fast something happens. Linear Motion. Motion on a straight path Scalar- Distance and speed Vector – Displacement and velocity. Motion is Relative.

fauna
Download Presentation

LINEAR MOTION

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. LINEAR MOTION Chapter 2

  2. Motion • Everywhere – people, cars, stars, cells, electricity, electrons • Rate = Quantity/time • How fast something happens

  3. Linear Motion • Motion on a straight path • Scalar- Distance and speed • Vector – Displacement and velocity

  4. Motion is Relative • Everything moves • Things that seem at rest are moving in relation to stars and sun • Book on a desk moves at 30 km/sec in relation to the sun • Same book is even faster in the galaxy • In this chapter – we look at motion compared to earth

  5. Speeds • Snail - 2 meters/day • Indy racecar – 300 km/hr • Space shuttle – 8 km/sec

  6. Speed • Distance / time • “per” – divided by – “/” • Any combination of units is useful depending on situation • Km/hr, cm/day, light-years/hour • Most common – m/sec and mile/hr

  7. Average Speed • Total distance/time interval • Examples: • 60 km in 1 hour = 60 km/hr • 240 km in 4 hour = 60 km/hr • Note the units • Does not indicate all the stops and starts

  8. The longer the time period measured, the more it leads to calculating an average velocity.

  9. Constant Speed • If the speed does not change over a long period, it is like Average speed • Length = velocity x time • l = vcont

  10. Instantaneous Speed • Speed at any moment • Speed can vary with time • Speedometer – measures instantaneous speed

  11. Chapter Chapter Assessment Questions 2 Question 2 Refer the adjoining figure and calculate the distance between the two signals? • Insert graph • 3 m • 8 m • 5 m • 5 cm

  12. Chapter 2 Chapter Assessment Questions Answer 2 Answer:C Reason:Distance d = df – di Here, df = 8 m and di = 3 m Therefore, d = 8 m  3 m = 5 m

  13. Questions • The speedometer in every car also has an odometer that records distance: • If the odometer reads zero at the beginning of the trip and 35 km a half-hour later, what is the average speed? • Would it be possible to attain this average speed and never exceed 70 km/hr? • If a cheetah can maintain a constant speed of 25 m/s, it will cover 25 meters every second. At this rate, how far will it travel in 10 seconds? In one minute?

  14. Graph of Constant speed • Average speed is the slope of the line during an interval • If it is a curve, the instantaneous speed is the line tangent to the curve at that point

  15. Delta Notation • Δ – Greek capital letter – Delta • Signifies a change in a quantity Δl = l f – l i Δt = t f -t i v = Δl = l f – l i Δt t f - t i

  16. Velocity • EDL (every day life) – speed and velocity are interchangeable • Physics – Velocity – speed in a direction • 60 km/hr North • Question – The speedometer of a car moving northward reads 60 km/hr. It passes another car that travels southward at 60 km/h. Do both cars have the same speed? Do they have the same velocity?

  17. Constant Velocity • Constant speed and direction • Must move in a straight line • Curves change the direction • Changing velocity- in a car there are 3 things to change velocity – • Gas • Brakes • Steering wheel

  18. The Displacement Vector • Displacement is the straight-line shift in position from Poto Pf • Included length and direction • Vector • Magnitude • Direction

  19. Resultant • The vector that is drawn between two points Resultant

  20. Vector Algebra • Rules for dealing with vectors • Helps us understand how to manipulate them

  21. Tip-to-Tail Method • Add vectors by placing tip of one to the tail of the other. • The resultant is from the tail of one to the tip of another A B B A Resultant

  22. Tip-to-Tail Method • Order of addition is irrelevant B A A B B A

  23. Parallelogram Method • Use 2 set vectors to make a parallelogram • The diagonal is the resultant

  24. Multiple Vectors • Add more than 2 vectors by the tip-to-tail method Resultant Resultant

  25. Parallel Vectors • Parallel – Simple sum • Anti-parallel (opposite directions) - Difference Resultant Resultant

  26. Acceleration • How fast is velocity changing • Acceleration is a RATE (of a rate) • Change in velocity • Acceleration • Deceleration • Change in direction • Acceleration = Change in velocity/time

  27. Question • Suppose a car moving in a straight line steadily increases its speed each second, first from 35 to 40 km/h, then from 40 to 45 km/h, then 45 to 50 km/h. What is its acceleration? • In 5 seconds a car moving in a straight line increases its speed from 50 km/h to 65 km/h, while a truck goes from rest to 15 km/h in a straight line. Which undergoes greater acceleration? What is the acceleration of each vehicle?

  28. Average Acceleration a – acceleration (m/s^2) v – velocity (m/s) t – time (s)

  29. Average acceleration problem Problem – What is the acceleration of a car the screeches to a stop from 96.54 km/h in 3.7 seconds?

  30. Instantaneous Acceleration • Velocity vs. Time graph • Slope of line tangent is equal to ACCELERATION • Sign of Slope • Positive – accelerating • Negative - decelerating

  31. Velocity-Time Graph of Accelerating Car Tangent Slope = acceleration velocity time

  32. Uniform accelerated motion • In the real world, acceleration is seldom constant • In problems, we can consider it constant for a few moments • Motion is in a straight line • Vf – final velocity • Vi – initial velocity

  33. Uniform accelerated motion • vf = vi + at • Problem – What is the final speed of a bicyclist moving at 25.0 km/h who accelerates +3.00 m/s^2 for 3.00 sec?

  34. The Mean Speed • What is vav for an object that is uniformly accelerating from vi to vf? Mean speed = vav = ½ (vi + vf)

  35. Area under the Graph • Equals the total distance moved Area of a retangle = m/s x s = Meters

  36. More complex • Area under still equals distance

  37. Mean Speed Theorem s = ½ (vi + vf) t Problem- A bullet is fired with a muzzle speed of 330m/s down a 15.2 cm barrel. How long does it take to travel down the barrel?

  38. Constant Acceleration Equations THE BIG FIVE • vf = vi + at • vav = ½ (vi + vf) • s = ½ (vi + vf) t • s = vit + ½ at² • vf² = vi² + 2as

  39. When vf is unknown • One sports car can travel 100.0 ft in 3.30 seconds from 0m/s. What is the acceleration?

  40. When t is unknown Problem – What is the cheetah’s acceleration if it goes 0 to 72 km/hr in 2.0 seconds? - How far will it go to be moving 17.9 m/s?

  41. Freefall – How Fast • An apple gains speed as it falls • Gravity causes acceleration • EDL – air resistance effects freefall acceleration

  42. Freefall Elapsed Time Instant. Speed (m/sec) 0 0 1 10 2 20 3 30 4 40 t 10t

More Related