motion and vectors regents

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?