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“The end is near! Just around the corner, turn left and then two rights ”
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SCALAR A quantity that has MAGNITUDE (size), and UNITS but NO direction. Ex: distance (d = 10 km), time (t = 2 min), speed (v = 25 m/s) VECTOR (symbolized by arrow) A quantity that has MAGNITUDE (size), UNITS, and DIRECTION. Ex: displacement (d = 10 km [E]), velocity (v = 25 m/s [N])
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DISTANCE (symbol: d) Distance is a scalar quantity. Measured in m or km. A measure of the TOTAL TRAVEL of an object, regardless of direction. Example: Andrew walks for 100 m on a circular track, and then runs for 400 m back to the start position. What is his total distance travelled? d 1 = 100m d 2 = 400 m d T = d 1 + d 2 = 500 m
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DISPLACEMENT (symbol: d)LINKLINK Displacement is a vector quantity. Measured in m or km. A measure of the shortest path from start point (aka reference point) to finish point; straight line path. Example: What is Andrew’s displacement? d T = 0 m His start and finish point are the same point.
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Which colour arrow(s) represents: Distance? Displacement?
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REFERENCE POINT Original start position “0”, all directions are given from the reference point. Ex: 0d = 2 m [E] POSITION An object’s displacement from the reference point. If more than 1 position, use symbols d 1, d 2, d 3,etc. 2 m REFERENCE POINT POSITION
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The red arrow represents the displacement Notice that distance is the entire route travelled.
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Reference Point? Distance? Displacement?
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SPEED (symbol: v) Speed is a scalar quantity. Measured in m/s or km/h. A measure of the distance per unit time. TYPES OF SPEED: Constant speed Instantaneous speed Average speed
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Example: Super Physics Guy (SPG) flew to Corner Brook from St. John’s, a distance of 750 km [W] in a time of 4.6 h. He then went to his friend’s house, 100.0 km [E] in a time of 15.0 min. What was his average speed?
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VELOCITY (symbol: v) Velocity is a vector quantity. Measured in m/s or km/h. A measure of the displacement per unit time.
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Example: In the above example, what was SPG’s average velocity?
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Acceleration can be a SCALAR or VECTOR quantity. Measured in m/s 2 or km/h/s. A measure of an object’s change in speed OR velocity per unit time.
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What are some typical descriptors we use for direction? Draw these on your sheet. N W S E D RL U X Y Z
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1-DIMENSIONAL VECTORS are vectors in the SAME PLANE. EXAMPLE: X PLANE: 2 m [E], 5 m [L] Y PLANE:3 m [D], 6 m [N] Notice that directions are always expressed using SQUARE BRACKETS. Example: 25 m [N25 o E] When calculating vectors in 1-dimension, we simply assign positives (+) and negatives (-) to our direction systems. POSITIVE is always assigned to: [N], [U], [E], [R] NEGATIVE is always assigned to: [S], [D], [W], [L] We can then calculate RESULTANT or TOTAL displacement by adding together our positive and negative individual vector values.
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DRAW A SKETCH! !!!!!!!!
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Example 1: McLennon is at his locker when the bell rings and he goes 20.0 m [E] to Science 1206 class. He does not have his homework done, so he then goes 50.0 m [W] to the office. What is his total displacement?
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Example 2: Anna goes 20 m [U], 15 m [D], 30 m [U], and 5 m [U] on a rock wall. What is her resultant displacement?
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Example 3: A Codroy Valley WILD BALONEY was sighted running through the forest. It ran 45 km[E], and then 65 km[W] in 2 hours and 15 min. What was its DISTANCE? AVERAGE SPEED? DISPLACEMENT? AVERAGE VELOCITY?
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Please complete WORKSHEETS 21 & 22 on pages 51 and 52 for homework.
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WHAT IS A VECTOR? An arrow that accurately indicates SIZE and DIRECTION of motion. It has a TIP and a TAIL. EXAMPLE: There are 2 types of vectors: POSITION VECTOR RESULTANT VECTOR TAIL TIP
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POSITION VECTOR Vectors that are connected to each other, starting at reference point, using the tip-to-tail method. EXAMPLE: RESULTANT VECTOR – (Hint: draw as a dashed or double line) The resultant vector indicates the resultant displacement or velocity. It is ALWAYS DRAWN from reference point (start) to finish. It indicates our CHANGE in POSITION from START to FINISH (the way the crow flies!). For the resultant vector, DIRECTION is always indicated FROM the reference point. EXAMPLE: d1d1 d2d2 d1d1 d2d2 dRdR d1d1 d2d2 Add vectors tip to tail. Resultant vector drawn from reference point to end point
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STEPS Indicate VECTOR DIRECTION using a bearing system. Example: Use a SCALE to indicate RELATIVE SIZE of vectors. Try to use a scale that is easily converted. EXAMPLE: 1 cm = 10 km Create a REFERENCE POINT and use a PROTRACTOR, RULER, and your SCALE to start your first POSITION VECTOR.
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STEPS... Connect remaining VECTORS using TIP-TO-TAIL METHOD. Draw RESULTANT VECTOR from REFERENCE POINT (START) to FINISH. Measure resultant vector size and angle to determine resultant displacement or resultant velocity.
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20 km [E] 20 km [N] 20 km [E20 o N] (reads “East 20 degrees North”)
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2.0 m [N] + 5.0 m [S] 250 m [S] + 400.0 m [W]
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48 km [E40 o S] + 30.0 km [W]
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500.0 m [N] + 1500 m [S50 o E]
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0.50 km [N20 o E] + 0.30 km [W] + 0.80 km [W50 o S]
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Please complete WORKSHEETS 23 & 24.
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Closed Book Test on Unit 3 Part 2 Booklet Topics include: Acceleration Speed-Time Graphs Vector and Scalar Comparisons Distance vs. Displacement Average speed vs. Average velocity Vector Diagrams Test Format: Multiple Choice Acceleration Calculations Speed-Time Graph Vector Diagram TEST DATE :______________
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