Post on 01-Jul-2015
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
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
Which person traveled the greatest distance?
Which person had the greatest displacement?
Vectors are represented by an arrow
- the length represents the size or magnitude
- the angle represents the direction
Vector AdditionResultant: the term given for the final sum vector when adding 2 or more vectors togetherQuestion: 4 cm + 5 cm = ?
WRONG!!!
4 cm north + 5 cm north = ?
9 cm north
4 cm north + 5 cm south = ?
1 cm south
I walk 3 blocks south, 4 blocks east and 3 blocks north.
a)What is my distance covered?
b)What is my displacement?
How does the displacement of a moving object compare to its distance covered?
Displacement <= distance
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?
Adding vectors – the parallelogram method
also called the Tip to Tail Method
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.
Resultant = 145 +/- 5
Direction = 15o
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.
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
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?
Average speed = 60 mile/hour
Unit for speed in SI system is meters/second
Convert this speed to meters/second
1 mile = 1609 m1 hour = 3600 s
Instantaneous speed- speedometer
Is speed a scalar or vector?Scalar
Velocity- speed with a direction- vector
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/sd = 18.3 m
t = 0.46 s
Impossible!!!
A horn is sounded and the echo returns in 4 s. How far away is the wall?
Thrust SSC
763 miles per hour
Car 1 goes from 0 to 60 mph in 7 secondsCar 2 goes from 0 to 60 mph in 3 seconds
Which car is faster?
Acceleration- the rate of change of velocity
= ?
= v f - vi v f – final velocity vi - initial velocity
Car 2vi = 0vf = 27 m/st = 3 sThe SI unit for
acceleration is m/s2
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?
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?