Ms. Mitchell’s 6th Grade

Greenbriar West Elementary

2007-2008

Matter

Topics

• Mass • Force

– Gravity– Weight– Tides– Our Solar System

• Energy– Potential Energy– Kinetic Energy

• Power

Mass

• What is mass?

• Does a party balloon have more mass than a candy bar?

• How do you figure out an object’s mass?

Force – Key Points

• What is a force?

• Why does gravity exert a force on you?

• If an object is not moving does that mean that there are no forces on it?

ForcesThe cool car is in my driveway.

Are there any forceson the car?

If so, draw them.

driveway

Gravitational Force - Questions

• So what causes a gravitational force?

• Is there a gravitational force on the moon?– Is it larger or smaller than the gravitational

force on the Earth?

Universal Law of Gravitation

• F = m (GMe/Re2) = mg (i.e. weight)

– Where• F = force on an object with mass, m

• G = gravitational constant = 6.7 x 10-11 m3/kg*s2

• Me = mass of the Earth = 5.94 x 1024 kg

• Re = radius of Earth = 6.38 x 106 m

• g = acceleration due to gravity = 9.81 m/s2

• Circle the terms above that are constants

Acceleration Due to Gravity

• There is a force exerted on an object as the result of the mass of the Earth– Therefore, the object is accelerated (I.e. the speed

increases) when released

At time = 0 seconds, an object is released with no velocity

One second later, it is going 9.81 meters/second

Therefore, the acceleration due to gravity is 9.81 meters/second per second which is the same as 9.81 m/s2

Gravitational Force

• Gravitational force keeps us “stuck” to the Earth!!!• We actually pull on the Earth but the Earth is too big to move!!!

Earth

Person

F

F

Fperson = FearthHow much you weigh depends on your mass and the mass of the planet you are on.

Weight vs Mass• Weight is a force: W = m g

m = mass and g = acceleration due to gravity = 9.81 m/s2

m (kg) W (Newtons)

10 98

5 49

12 118

5 52

18 177

5 47

8 78

Mass, kg

Wei

ght,

New

tons

0 2 4 6 8 10 12 14 16 18 20

40

020

6080

100120140160180

PLOT THE DATA!!

Review of Science Terms

• Constant – _____________________________

• Variables – _____________________________

• Independent Variable – ___________________

• Dependent Variable – ____________________

Gravitational Force - Questions

• Is there a gravitational force on a person standing on the moon?– Is it larger or smaller

than the gravitational force on the Earth?

– Why?

How the Moon Causes Tides

• Since the water in the oceans are liquid they are pulled out of shape by the moon’s gravitational force– Causes water level to rise thus creating tides (i.e. water

seemingly getting deeper and shallower for no apparent reason)

Earth Moon

Water bulging up

Our Solar System

• The Sun is the center of the solar system– Why is it the center?– Why is it useful to have the Sun as the center?

• Nine planets orbit the Sun– Inner planets are small and rocky

• What are they?

– Outer planets are large and gaseous (mostly)• What are they?

Our Solar System

• Inner Planets– Mercury

– Venus

– Earth

– Mars

• Which planet is hottest?

• Which planet is coldest?

• Does this make sense?

• Outer Planets– Jupiter– Saturn– Uranus– Neptune– Pluto

• How do you think Pluto was added to our solar system?

Inner Planets

• The time it takes for a planet to orbit the Sun (i.e. orbital period) is proportional to how far the planet is away from the Sun.– Will it take more or less than a year for Venus to orbit the Sun?

Asteroid Belt• Asteroids are rocky and metallic objects

that orbit the Sun but are too small to be considered planets.

– Range in size from pebbles to as large as 1000 km

– Sixteen asteroids have a diameter of 240 km or greater.

• Most asteroids are contained within a main belt that exists between the orbits of Mars and Jupiter.

– Some have orbits that cross Earth's path and some have even hit the Earth in times past.

• Asteroids are material left over from the formation of the solar system…

Outer Planets

- How do the outer (or Jovian) planets differ from the inner (or terrestrial) planets?

Planets By Size !!!!!!

• Mars is the same mass as Earth but half the size – what does that tell you about the density of Mars?

• Jupiter weighs more than any other planet – twice as heavy as the nest most massive (Saturn).– On which planet would you weigh the most – or would you weigh the same on

every planet?

Potential and Kinetic Energy

• What is energy?

• What is potential energy?

• What is kinetic energy?

Potential Energy

Does the boxhave any storedenergy here?

Does the boxhave any storedenergy here?

Potential Energy

What happens when we let goof the box?

If the box is to move show the direction of the box.

Label the forces on the box!!!!

Work, Energy, and Power

• Review: Force is a push or a pull– Exerting a force over a distance is WORK

• For example, pushing the desk across the room is “a lot of work”

– ENERGY is the ability to do work• For example, a compressed spring has the ability to push some object

a distance

– POWER is the consumption of energy over time• For example, power is consumed when a light bulb is left on for a

period of time (light bulb dissipates energy)

Quick Review of Science Facts

• Force - ___________• Work - ___________

____________________• Energy - __________

___________________• Power - __________

___________________

___________________

• Constant – ___________

______________________• Variables – ___________

_______________________• Independent Variable –

_____________________• Dependent Variable – ___

_______________________

_______________________