Lesson 3

Why does your motor spin?
You will need your motor and a compass.
The compass is not provided in the Inventions Kit.

1 What did you do last time? 2 balance scale gravity inertia weight mass grams PRINT the word next
to the image on the next slide.
3
PH-lesson L5 ma me in gr gr bal
4 INERTIA You have explored the idea of INERTIA. The greater the mass,
the greater the force it takes to overcome the inertia.
An object at rest
stays at rest
unless acted upon
by an unbalanced force.
An object in motion
stays in motion
unless acted upon
by an unbalanced force.
5 MASS The amount of matter
that you are made of
is called your mass!

You are made of the same amount of mass whether you are on the Earth, the Moon or in outer space.

Your weight is dependent
on the pull of gravity,
your mass is not.

How do you measure mass
independent of gravity
You have explored the idea of mass. You measure mass
with a balance scale!
You have explored the idea of force.
FORCE a push or a pull A force
is a push
or a pull.
What is a
unit of
measurement
for force
You can measure
force in newtons!
7 GRAVITY is an invisible FORCE
that PULLS objects toward each other.

Earth's gravity keeps you and
penguins on Antarctica
on the ground.
It makes objects like apples
fall down to Earth.

Your weight is a measure of
the PULL of gravity on Earth.
If you go to the Moon,
does your weight or mass change
Albert Einstein described gravity
as being due to a curvature of space
that warps space around an object,
such as a star or a planet.
Attribution: The King's School Gratham Your weight will be LESS.
Your mass remains the same.
8 Let's explore motion! Speed
Velocity
Acceleration
9 You will need: How fast can you run
from one end to the other?
Calculate You Speed! stop watch or
stop watch app
Measure
the length of
a long hallway
or path.
tape
measure
1
10 SPEED is the distance you ran in the time you took to run it.
What was your SPEED?
Clock your time with a stopwatch
or cell phone application.
2 READY, SET, GO!
11 and the time it took you to run that distance was 1 second, (or 3 meters per second) then your SPEED was
10 feet per second.
from start to finish
was 10 feet (3m)
3 4 If the distance you ran
12 SPEED speed = distance / time 13 Click for
answer.
If you run 50 feet
in 10 seconds,
what is your speed
Your speed equals 50 feet divided by 10 seconds. 5 feet per second
14 ONE HOUR What is the SPEED limit
for driving in your neighborhood?

Is it 25 miles per hour (mph) or
40 kilometers per hour (kph)?

If you go the speed limit,
how long will it take your car
to go 25 miles (40 kilometers)
30 minutes What is the SPEED limit on your highways?

Perhaps it is
70 mph or
as much as 120 kph.

If the speedometer in your car reads 60 mph,
how long will it take your car to go 30 miles
16 The SPEED of a passenger jet
is about 600 mph or 965 kph.

About how many hours would it take
to fly 3,000 miles or 4,825 kilometers
Walking speeds vary greatly depending on height, weight, age,
terrain, surface, load, culture, effort, and fitness.
The average adult walking speed at crosswalks is about
5.0 kilometers per hour (km/h),
or about 1.4 meters per second (m/s),
or about 3.1 miles per hour (mph).
What is your SPEED when you walk 5 hours
17 6 trillion miles (9 trillion km).
That is a 6 with 12 zeros after it!

It is also ONE light year.
The SPEED of light is
186,000 miles per second (mps)
or 300,000 kps.

How many miles
can light travel in a year
18 Measuring Speed 19 Both SPEED and velocity measure distance over time.
BUT velocity ALSO measures something ELSE!

To figure out what else velocity measures,
let’s clock your speed again.
VELOCITY
20 Can you make yourself run
the SAME distance
first up the path
and then back down the path
in EXACTLY the same
amount of time?
Suppose it took you EXACTLY three seconds to go up the path
and EXACTLY three seconds to come back.

Your SPEED would be the same in both directions
but your velocity would be different!

Can you guess what makes velocity different from speed?
21 tells you NOT ONLY your SPEED BUT ALSO your VELOCITY DIRECTION! DIRECTION! DIRECTION! 22 Changing your direction may not change your SPEED,
but it always changes your velocity.
Velocity measures
both speed and direction!
23 Did you notice how difficult it was
to go at a constant, unchanging speed?
Sometimes you
sped up.
Sometimes you
slowed down.
Your speed was an average.
It was neither your slowest nor your fastest time.
Your speed and velocity were changing from moment to moment as you ran.
acceleration! This change in velocity is called
24 Acceleration is a change in velocity. Speeding up is
an acceleration!
Slowing down is
an acceleration
(deceleration).
Changing direction
is also an acceleration!
Accelerate, Accelerate!
25 Acceleration 26 Does an object
with more mass
also have more inertia
What is a unit of mass Is your mass zero in outer space You measured
weight with a
1 2 3 4 5 You measured mass with a spring meter YES! grams or kilograms NO. You will be weightless but
not massless. You will still be
made of the same amount of matter.
balance scale
27