Ideas

Ideas

Ideas

**Speed, Velocity and Acceleration!**

~~Fire Starter!~~

What do you already know?

Calculating Motion

Speed, Velocity and Acceleration:

Describing Speed: Sp=d/t

Who is faster Usain Bolt or a Cheetah

Velocity:

V=d/t

The only difference between Speed

and Velocity is the

new component of

Direction.

Acceleration : A=v/t

The rate at which the velocity of an object is changing

Question 1:

What do you know about speed?

Describe speed the best you can.

Question 2:

What about Velocity; tell me what you know about velocity.

QUESTION 3

Finally tell me about Acceleration.

The big questions:

How can I calculate motion?

How do i tell the difference from speed and velocity; and from velocity and acceleration

Speed is

the distance an object covers in a certain amount of time

Velocity is

the distance an object covers in a given amount of time

.... in a certain direction.

The equation for average speed is:

Sp= d/t

d=distance

t=time

The equation for Velocity is:

V=d/t

V=Velocity

d=distance

t=time

Acceleration is

the rate at which velocity changes with time.

The equation for Acceleration is:

A=v/t

A=acceleration

V=velocity

t=time

Bolt holds the world record in the 100 meter dash.

Sp.=d/t

Sp.=100m/9.58s

Bolt runs an average speed of 10.43 meters per second

The Cheetah holds the record for the fasts burst of speed for a mammal.

Sp.=d/t

Sp.=100m/6.10s

The cheetah's average speed is 16.39 meters per seconds

Any combinations of units for distance and time can be used to describe speed.

Example: Kilometers per hour , centimeters

per day , meters per second

Note :

The metric system unit for speed is m/s.

YAAAYYYY FINN and Jake are Back

MMMM BRAINS

Finn and Jake are being chased by a brain crazy zombie.

The zombie is able to run at 5m/s

AHHHHH

Zombie

If the zombie is able to run 5m/s, Finn and Jake must run at least 6 m/s.

How long must it take them to run a distance of 450m to escape the zombie?

To solve the problem:

Write the equation we are going to use.

Sp=d/t

Next input the numbers we know.

6m/s=450m/t

Solve the equation: t= 450m/6m/s

t=75s

There are two types of speed we can measure

Instantaneous Speed:

The speed of an object at any instant.

Average Speed:

The total distance traveled by an object divided by the

total time it took.

In this class we will use average speed:

Av.Sp.=df-di/t

Ex: We can see instantaneous speed anytime we are traveling in a car by looking at the speedometer. That is the speed we are moving in a vehicle at a given point in time.

Speed

is a

scalar quantity

. It has only

magnitude. It can be represented by a single number.

Velocity

is a

vector quantity.

It has both magnitude and direction. It can be represented by a number and an angle on a coordinate plane.

Increasing velocity is represented by a green arrow.

Decreasing velocity is represented by a blue arrow.

X) Two escalators next to each other going up and down. Each has a speed

of 2 km/h.

Because their direction is opposite, they have different Velocities.

1) If an object continues in the same direction, but

speeds up or slows

down,

it’s velocity has changed.

2) If an object continues at the same speed, but

changes direction

, its

velocity has changed.

Ways to Change Velocity:

Riddle

me

this

?

?

?

?

?

?

?

I can run as fast as possible for as long as I like.

I will never change speeds, but my velocity always changes. Why?

Because I am running around a track and my direction always changes.

This is a measure of how the velocity of an object changes with respect to time.

Acceleration =change of velocity

time

The types of of acceleration:

1) speeding up – positive acceleration

2) slowing down – negative acceleration

3) changing direction.

Another way to think about acceleration is:

Acceleration =

final speed - initial speed

time

Practice with Acceleration!

X) Suppose a jet starts at rest at the end of a runway. As it takes off, it reaches a

speed of 80 m/s in 20 s.

(Straight down the runway, its speed and velocity are the same.)

Acceleration =

final speed - initial

time

PUT THEM IN THE EQUATION

**Sp=d/t**

**A=V/t**

Quiz time

MOTION!

Speed, Velocity & Acceleration!

How to describe motion using Speed, Velocity and acceleration.

Key Equations:

Av.Sp.=df-di/t

V=d/t

A=vf-vi/t

Key Vocabulary:

Speed

Instantaneous Speed

Average Speed

Velocity

Scalar

Vector

Acceleration

Vocabulary and Equations

Two examples of how to calculate speed when given the Distance and the time.

TRY TO FIND HOW FAR BOLT COULD RUN IN 60 SECONDS IF HE STAY AT THE SAME SPEED THE ENTIRE TIME.

STEP 1: WRITE THE EQUATION:

SP=d/t

STEP TWO: FIND ALL GIVEN VARIABLES:

SP=10.43m/s & t=60s

Step 3: What is the unknown:

d=distance

STEP 4: PUT VARIABLES INTO EQUATION:

10.43m/s= d/(60s)

STEP 5: SOLVE EQUATION:

625.8m

A scalar quantity is a quantity that just gives magnitude or how much of something.

ex: temperature, speed, how much something cost. Austin is 32 miles away.

A vector quantity is a something that not only tells us the how much part, but also tells me in what directions:

ex: velocity, Austin is 32 miles NORTH

What we know:

Vf=80m/s

vi=0m/s

t=20s

What we don't know:

ACCELERATION

A=vf-vi

t

A=80m/s-0m/s

20s

A= 80m/s

20s

Solve the equation

A=80m/s

20s

A=4m/s

**V=d/t**

**Be prepared at the start of the next class for 5 question!!!!!**