2. All physics quantities fall into one of two
categories:
Scalar – a quantity that can be described with a
single number (size, magnitude).
Ex. I drove 15 miles.
This is the quantity known as distance
3. Vector – a quantity that includes a number and a
direction.
Ex – I drove 10 miles south.
This quantity is known as displacement
Displacement can be defined two ways
1) distance traveled in a particular direction
2) final location relative to a starting point
4. Which person traveled the greatest distance?
Which person had the greatest displacement?
5. Vectors are represented by an arrow
- the length represents the size or magnitude
- the angle represents the direction
6.
7. Vector Addition
Resultant: the term given for the final sum vector when
adding 2 or more vectors together
Question: 4 cm + 5 cm = ?
WRONG!!!
4 cm north + 5 cm north = ?
9 cm north
4 cm north + 5 cm south = ?
1 cm south
8. I walk 3 blocks south, 4 blocks east and
3 blocks north.
a)What is my distance covered?
b)What is my displacement?
9. How does the displacement of a moving object
compare to its distance covered?
Displacement <= distance
10. A duck walks 60 m north and then 40 m
east. Using a scale of 1 cm = 10 m, draw
the displacement vectors of the duck.
What is the resultant displacement?
What is the angle between the resultant
and north?
11. Adding vectors – the parallelogram method
also called the Tip to Tail Method
12. Add two vectors:
100 mi east
50 mi at 45o north of east
Find the length and direction of the
resultant using a ruler and protractor.
14. A = 80 mi west
B = 60 mi at 45o south of east
A+B=?
Find the length and direction of the
resultant using a ruler and protractor.
15.
16. Using the scaled vector process, find the
magnitude and direction of the
following resultants:
1)50 m N + 30 m E + 40 m N
2) 5 m E + 5 m northwest + 10 m S
17. Speed – a measure of how fast something moves
- the rate at which distance is covered
You drive 180 miles in 3 hours. What is your
average speed?
18. Average speed = 60 mile/hour
Unit for speed in SI system is
meters/second
Convert this speed to meters/second
1 mile = 1609 m
1 hour = 3600 s
19. Instantaneous speed
- speedometer
Is speed a scalar or vector?
Scalar
Velocity
- speed with a direction
- vector
20. A baseball is thrown at 90 mi/hr. How long
does it take to travel the 60.5 ft from the
pitcher’s mound to home plate? (3.3 ft = 1 m)
v = 40 m/s
d = 18.3 m
t = 0.46 s
Impossible!!!
21. A horn is sounded and the echo
returns in 4 s. How far away is
the wall?
24. Car 1 goes from 0 to 60 mph in 7 seconds
Car 2 goes from 0 to 60 mph in 3 seconds
Which car is faster?
Acceleration
- the rate of change of velocity
=?
25. = v f - vi v f – final velocity
vi - initial velocity
Car 2
vi = 0
vf = 27 m/s
The SI unit for
t=3s
acceleration is m/s2
26. Constant speed or velocity
“cruise control”
a=0
An airplane slows from 200 m/s to 50
m/s in 12 seconds. What is its
acceleration?
27. An airplane accelerates from a standing
start at 2.5 m/s2. After 7 s,
a)How fast is it moving?
b)How far has it travelled?
