# More Kinematics!

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14 Νοε 2013 (πριν από 4 χρόνια και 7 μήνες)

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Kermit Learns

Kinematics Quantities

Don’t let the
details leave
you in the
dust!

KL physics 10

Kinematics is…

The physics of
how

an object moves:

How

far

does it go.

How

fast
does it go.

How

fast

it gets faster or slower.

How

long
does it take.

Vector

Scalar

Distance

Displacement

Speed

Instantaneous Speed

Velocity

Acceleration

Watch for these vocabulary words.

Vector and Scalars, Huh?

Magnitude

a measure of the size, amount or quantity of an object
(how many, how much)

Example:
Sai

wears an
extra large
t
-
shirt

My physics book has a
mass of 3 kg
.

Scalar
-

a quantity that has
magnitude

only.

Example: I waited for
30 minutes
.

He
drove
75 mph
.

Vector

a quantity that has
magnitude

and
direction
.

Example: You drive
50 miles
east
.

The plane flies
300 mph
south
.

Distance vs.
Displacement

How far did it travel?

Start

Finish

distance

Displacement

is the difference in
position from start to finish.

The symbol is
𝑑

.

The unit for displacement is meters

Distance
is the length of the path
from start to finish.

The symbol is d.

The unit for distance is meters

An object travelling in only one direction will have the same distance and displacement.

Speed
vs

Velocity

How fast is it moving?

Speed

Velocity

A measure of how fast an object’s
position changes.

A measure of how fast

an object position
changes and the direction of motion

The ratio of distance traveled to time
interval

Velocity is the ratio of displacement to
time interval

Scalar (magnitude only)

Vector (magnitude and direction matter)

The symbol for speed is v

The symbol for velocity is
𝑣

Measured in units of m/s.

Velocity is measured in units of m/s

An object traveling in one direction only will have the same speed and velocity.

Instantaneous Speed

Good news! No equation!

This is the speed at a single instant in
time.

When you check your speedometer
you are checking instantaneous
speed.

Kermit wants to know…

What if I want to change my speed?

Possible responses:

Too bad for you.

Why would you do that?

Isn’t this speed good enough?

What do you mean?

I’m sure there’s some physics to
learn about.

Acceleration

How fast did it get faster or slower

or did it turn the corner?

Acceleration

It is a change in velocity.

(speed and/or direction)

Vector (direction and magnitude)

The ratio of velocity to time interval

The symbol for acceleration is
𝑎

.

Acceleration is measured in units of m/s
2
.

If an object is speeding up, slowing down or changing direction it is accelerating.

Apply this to your life…

When you are riding in a car think about how
the direction and speed are changing as the car
moves along.

Is the speed constant?

Is the direction changing?

Is the velocity constant?

Is the
car accelerating?