# Grade 10 Science (PowerPoint) by gjjur4356

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```									    Grade 10 Science

Motion Unit
Significant Digits
   The correct way to record measurements is:
   Record all those digits that are certain plus one and no
more
   These “certain digits plus one” are called significant digits
   ALL DIGITS INCLUDED IN A STATED VALUE (EXCEPT

Measurements
Examples
Table 1 Certainty of Measurements
Measurement                        Certainty
(#of Significant Digits)
307.0 cm                             4
61 m/s                             2
0.03 m                             1
0.5060 km                            4
3.00 x 10 8 m/s                        3
2340.00
0.1240
2005     Decimal
Absent

Decimal
Present
0.003450

A Red Arrow pops the 0’s             2500
like balloons until it sticks in
a digit between 1 and 9.
Then you count the rest of
the digits that are left.
Counted and Exact Values

        When you count the number of something (example –
students in the class), this is an exact value and has an
infinite number of significant digits.
        When you use a defined value such as 100 cm/m or 60
s/min, you also have an infinite number of significant
digits.
   Note the calculation rules on BLM 9.2B
Converting Units

   When you want to change                  100cm/m
units we use a conversion
factor (or equality)                     1000m/km
Some
Equalities   60 s/min

60 min/h
Assignment : Significant Digits

   BLM 9.2a, 9.2b
   Complete the Significant Digits Worksheet See
   Questions 1-6, 9 pg 349 in your text
Relating Speed to Distance and Time

   Average Speed Vav is:
       The total distance divided by the total time for a trip
                      Vav =           d
                                      t
   See BLM 9.5a for examples
   Instantaneous speed – the speed an object is travelling at a
   Constant Speed (uniform motion) – if the instantaneous speed
remains the same for a period of time. Ie. Cruise control on your car
A car travels 45 km at a speed of 90 km/h.
How long did the trip take?
   What do you know in the Question
   d= 45 km
   Vav = 90 km/h
   t=?
   Decide on a formula
   t=    d
Vav                d

Vav       t
   Substitute the knowns into the formula and solve
   t     = 45 km
90 km/h

t = 0.5 h

•Write a concluding statement:

It takes 0.5 h for the car to travel 45 km at a speed of 90 km/h
Problem Solving Summary

   List the variables you know
   Decide on a formula
   Substitute what you know into the formula
   Solve and write a concluding statement

Speed- Click Me
Assignment : Relating Speed to
Distance and time

   BLM 9.5 a,b, d
   Questions 1,2,3,6,7,8 pg 358
Distance – Time Graphs

   Independent variable - X axis is always time
   Dependent Variable - Y axis is always distance
   Speed is determined from the slope of the best fit
strait line of a distance – time graph
   SmartBoard Slope of a Line
In the following diagram:
See BLM 9.7a A = constant speed
B = not moving
C = accelerating      Distance-Time Graphs
Assignment : Distance – Time Graphs
   Lab 9.5 Graphing Distances During Acceleration
   Questions 3,4,5,6 pg 365
   Activity 9.9 Simulation : Average Speed on an Air Table
   BLM 9.9a
   Worksheet – Determining Speed from a d/t Graph
   Q 1-6
   Lab9.6 Balloon Cars Lab
   Lab 9.10 Determining an Average Speed
   Review Questions 1,3,4,7,9,11 pg 376
   Test Chapter 9
Chapter 11 Displacement and
Velocity
Introduction to Vectors

   Reference Point – origin or starting point of a journey. Ie. “YOU ARE
HERE” on a mall map

   Position – separation and direction from a reference point. ie. “150 m
[N] of “YOU ARE HERE”

   Vector Quantity – includes a direction such as position. A vector
quantity has both size and direction ie. 150m [N]

   Scalar quantity – includes size but no direction. ie. 150 m
Symbol           Example
Quantity Symbol

Scalar Quantity

Distance                            292 km
d
Time                               3.0 h
t
Vector quantity
2 km [E] (from
Position
d               Subway)

Displacement
d          292 km [S]
   Displacement – a change in position.
   See BLM 11.1a
   Symbol Format – used when communicating a
vector.
   See BLM 11.1b
   Drawing Vectors –
   state the direction (N,E,S,W)
   Draw the line to the stated scale or write the size of the
vector next to the line
   The direction of the line represents the direction of the
vector and the length of the line represents the size of
the vector
Assignment : Introduction to Vectors

   Questions 1,5,6,7,8 pg 417
   Walk the Graph Activity pg 418 & BLM 11.2
Adding Vectors on a Straight Line
   Vector Diagrams – Join each vector by connecting
the “head” end of one vector to the “tail end of the
vector.
next vector.

   Find the resultant vector by drawing an arrow from
the tail of the first vector to the head of the last
vector

Resultant displacement -           dR
is a single displacement that has the same effect as
all of the individual displacements combined.
Adding vectors can be done by one of
the following methods

usingscale diagrams

combined method

 See   BLM 11.3
11.3 Adding Vectors Along a Straight Line

Two vectors can be added together to determine the
result
(or resultant displacement).

Use the “head to tail” rule
Join each vector by connecting the “head” and of a
vector to the
“tail” end of the next vector
d1
d2

dR
Resultant vector
Scale Diagram Method

Leah takes her dog, Zak, for a walk. They walk 250 m
[W] and then back 215 m [E] before stopping to talk to a
neighbor. Draw a vector diagram to find their resultant
displacement at this point.
Scale Diagram Method

1)State the direction (e.g. with a compass symbol)
N

2)List the givens and indicate the variable being solved
d1 = 250m [W], d2 = 215m [E], dR = ?
3)State the scale to be used
1 cm = 50 m
4)Draw one of the initial vectors to scale
to scale

6)Draw and label the resultant vector
dR

7)Measure the resultant vector and convert the length
0.70 cm x 50m / 1 cm = 35m [W]

8)Write a statement including both size and direction of
the resultant vector
The resultant displacement for Leah and Zak
Is 35 m [W].

This time Leah’s brother, Aubrey, takes Zak for a walk
They leave home and walk 250 m [W] and then back
175 m [E] before stopping to talk to a friend. What is the
resultant displacement at this position.
When you add vectors, assign + or – direction to the value
of the quantity.
(+) will be the initial direction
(-) will be the reverse direction

1.Indicate which direction is + or –
250 m [W] will be positive
2.List the givens and indicate which variable is being
solved

d1 = 250 m [W], d2 = 175 m [E], dR = ?
3.Write the equation for adding vectors

dR =      d1 +    d2

4.Substitute numbers (with correct signs) into the
equation and solve
dR = (+ 250 m) + (-175 m)
dR = + 75 m or 75 m[W]
size and direction)
The resultant displacement for Aubrey and Zak is 75 m [W]
Combined Method

Zak decides to take himself
for a walk.

He heads 30 m [W] stops,
then goes a farther 50 m [W]
before returning 60 m[E].

What is Zak’s resultant
displacement?
Combined Method

1)State which direction is positive and which is negative

West is positive, East is negative

2)Sketch a labeled vector diagram – not to scale but
using relative sizes
50m              30m

60m                  dR
3)Write the equation for adding the vectors

dR = d1 +d2 +d3

4)Substitute numbers( with correct signs) into the equation and
solve
dR = (+ 30 m) + (+50m) + (-60m)
dR = + 20m or 20m [W]

direction)

The resultant displacement for Zack is 20 m [W]
Assignment : Adding Vectors in a Straight
Line

   Questions 1-3,5-7 pg 423 Answer Key
   Activity “Bug Race”

      If we know the path an object takes we can draw an
accurate to scale vector diagram of the journey. We can
then determine the following;
   compare the final position to the reference point
   determine the resultant displacement
   Certain rules must be followed add vectors at an angle.
See BLM 11.5a

Scale 1 cm = 5 Km

d R = 5cm
dR = 5 cm x 5 Km/1cm
d 1 = 3 cm
dR = 25 Km [NW]
N

d 2 = 4 cm
Assignment : Adding Vectors at an Angle

   BLM 11.5b
   Activity “Hide a Penny Treasure Hunt”
Velocity

        Velocity –       v
   a vector quantity that includes a direction and a speed
ie. 100 km/h [E]

   Constant Velocity – means that both the size
(speed) and direction stay the same
   Average Velocity – v      av

is the overall change of position from the start to finish.
It is calculated by dividing the resultant displacement
(which is the change of position) by the total time
   V av      =       dR
t
   See BLM 11.7a,b
Assignment : Velocity

   BLM 11.7c
   Questions 3,5,7, pg 436
   Activity Tracking and Position pg 438 & BLM 11.9
   Review Questions 4,8,9,10 pg 442
   Test Chapter 11
Chapter 12 Displacement, Velocity,
and Acceleration
Position – Time Graphs

       Position and displacement are vectors and
include direction. It is possible to represent vector
motion on a graph. Very much like a distance –
time graph. Can you see the differences?
Can you see the differences?
   The slope of a position-time graph is equal to the
velocity of the motion

   The slope of the tangent at a point on a position-
time graph yields the instantaneous velocity.

   Instantaneous velocity is the change of position
over an extremely short period of time.
Instantaneous velocity is like instantaneous speed
plus a direction
Assignment : Position-Time Graphs

   Activity : Describing Position-Time Graphs “Walk
the Dog”
   Activity : The Helicopter Challenge
   Exercise : BLM 12.1 a,b,c
Velocity Time Graphs
   A velocity – time graph can show travel in opposite
directions over a period of time.

   The slope of the line on a velocity –time graph
indicates the acceleration of an object
   Acceleration – a
is calculated by dividing the change in velocity by
the time. Because there is a direction associated
with the velocity, the acceleration is also a vector
quantity.

   Constant acceleration is uniformly changing
velocity.
Formula

a   =     v

t
   Average Velocity of an object in motion can be
determined from the ratio of total distance divided
by total elapsed time.
V av   =        dR

t
See BLM 12.2 a,b
Assignment : Velocity – Time Graphs

   BLM 12.2 c
Acceleration and Displacement

   Acceleration is the change of velocity over time
   Questions 5,7,8 pg 465
   Test Chapter 12

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