# Part 2.  In previous learning we have looked at the differences between different vocabulary words in physics. Most notably:  Scalar vs. Vector  Distance.

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Part 2

 In previous learning we have looked at the differences between different vocabulary words in physics. Most notably:  Scalar vs. Vector  Distance Vs. Displacement

 Two words that have meanings that can be very similar are :  SPEED and  VELOCITY  What’s the fastest human speed? (2 videos)

 How fast an object is moving  Think of when we learned about distance, all we are doing is adding how much time it took to cover that distance.  A scalar, therefore there is no direction of motion.  Examples... ▪ 20 km/hr ▪ 40 m/s ▪ 1 mm/ms

 Speed in measured in 2 quantities: ▪ How fast an object is going in time (ex 10 km/hr)  In order to calculate speed in this time, we simply take the distance value (such as km or m) and divide it by the time value (such as hours or seconds).

SPEED = distance time

 Faster vs. Slower  When will the points be closer together? When the tape is pulled faster or when the tape is pulled slower?  Why is this?

 In groups of 2, grab a stop watch.  Decide on a set amount of distance, such as 10 steps or from one end of the room to another.  Have 1 person cover the distance, while the other person times how long it takes.  Reverse roles.  Try out your calculations and determine who has the fastest speed.

 Try out the following examples: 1) A car travels 140 km in a 2 hour time. What is its speed in km/hr? 2) A person Sam walks to school a total distance of 9.8 km. It takes him about 3.5 hours. What is his speed in km/hr? 3) A duck ran.03 km in.010 hours. What is its speed in km/hr?

 How fast an object’s position is changing.  Rate of change of position.  Think of when we learned about displacement, all we are doing is adding how much time it took to change the postion of the person.  Vector quantity, with both speed and direction.  Change in distance in change in time  Example: ▪ 140 m W in 10 seconds

 Velocity = the change in distance (or amount) the change in time (or amount)  ‘Change in’ can also be written as ∆ (delta).

VELOCITY = DISPLACEMENT CHANGE IN TIME

 In order to move an object, we must change the object’s position. Any change in position is called displacement.  Along a straight line, change in distance can be found by the final position minus the initial position.  Or  ∆d = position 2 (final) – position 1  Or  ∆d = d₂ - d₁

Example: A car moves across a table in a straight line. The initial position of the car is -1 cm. If the car stops at the +3 mark, calculate the displacement of the car.

-Calculate the displacement of each object: - CAR = -BICYCLE = -PEDESTRIAN = -SKATEBOARDER=

 In groups of 2, grab a stop watch.  Decide on a set amount of displacement, such as 10 steps from your seat or a lap around the room..  Have 1 person cover the displacement, while the other person times how long it takes.  Reverse roles.  Try out your calculations and determine who has the fastest speed.

 When dealing with compass direction (North, East, South and West) you must also qualify the directions as either positive or negative. + + - -

 An Interval of time or change in time.  How much time was used.  Most questions will give you a set amount of time. ▪ Example: Traveled for 3 hours = TOTAL TIME = 3 hours  However, if the question has more than 1 time value, you simply add them together ▪ Example traveled for 2 hours then 1 hour = TOTAL TIME = 3 hours

 Speed vs. Velocity  13 questions total, we will go through 1 and 2 together first.

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