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JOAN CARTAN-HANSEN: HI, I'M JOAN
CARTAN-HANSEN.
AND WELCOME TO SCIENCE TREK: THE
WEB SHOW .
AND WELCOME TO THE DISCOVERY
CENTER OF IDAHO.
JOINING US TODAY TO ANSWER YOUR
QUESTIONS ABOUT FORCE AND MOTION
ARE KATHRYN DEVINE, ASSOCIATE
PROFESSOR OF PHYSICS AT THE
COLLEGE OF IDAHO, AND JOHN
GARDNER, PROFESSOR OF MECHANICAL
AND BIOMEDICAL ENGINEERING AT
BOISE STATE UNIVERSITY.
THANKS FOR BEING HERE.
KATHRYN DEVINE: THANKS FOR
HAVING US.
JOHN GARDNER: THANK YOU.
CARTAN-HANSEN: OKAY, LET'S GO TO
YOUR QUESTIONS.
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RYDER: HI, MY NAME IS
RYDER, AND I GO TO OWYHEE-HARBOR
ELEMENTARY SCHOOL.
AND MY QUESTION IS WHAT IS FORCE
AND MOTION?
GARDNER: FORCE AND MOTION ARE
PART OF A FAMILY OF CONCEPTS
THAT HELP US UNDERSTAND JUST THE
BASICS OF THE WORLD AROUND US,
LIKE DISTANCE AND VELOCITY AND
TEMPERATURE.
AND "FORCE" IS THE WORD WE USE
TO DESCRIBE A PUSHING OR PULLING
ALONG A LINE OF ACTION, ALONG A
CERTAIN LINE.
AND "MOTION" IS THE RESULT OFF
OF THE RESULT OF A FORCE.
IT'S A BODY THAT CAN MOVE OR
THAT MOVES BECAUSE YOU'VE PUSHED
ON IT.
OR IT CONTINUES TO MOVE BECAUSE
NOTHING ELSE IS PULLING IT BACK.
CARTAN-HANSEN: MICHAEL WOULD
LIKE TO KNOW: HOW DOES FORCE
PULL THINGS DOWN INSTEAD OF UP?
DEVINE: WELL, IT DEPENDS ON THE
FORCE.
THE FORCE THAT MICHAEL'S
PROBABLY THINKING ABOUT IS THE
FORCE OF GRAVITY, WHICH IF YOU
KNOCK SOMETHING OFF THE TABLE,
IT GETS PULLED DOWN.
BUT THERE ARE A LOT OF FORCES
THAT PULL THINGS UP RATHER THAN
DOWN.
IF YOU'RE IN AN AIRPLANE, THEN
THERE'S THE LIFT FORCE FROM THE
WINGS PUSHING YOU UP, AND THAT'S
WHY YOU GO OFF THE GROUND.
IF YOU PICK YOUR COFFEE MUG UP
OFF A TABLE AND HAVE A SIP, THEN
YOUR ARM IS EXERTING A FORCE, A
PULL ON THE MUG THAT CAUSES THE
MUG TO GO UP.
AND SO FORCES CAN PULL IN ANY
DIRECTION.
IT JUST DEPENDS ON THE TYPE OF
FORCE.
THE REASON GRAVITY PULLS THINGS
DOWN IS BECAUSE WHAT WE
EXPERIENCE AS GRAVITY IS BECAUSE
THE PLANET EARTH HAS A LOT OF
MASS, AND THAT MASS EXERTS A
GRAVITATIONAL FORCE ON ALL OF
THE OBJECTS ON IT.
AND THE DIRECTION OF THAT FORCE
IS TOWARDS THE CENTER OF EARTH,
WHICH WE CONSIDER DOWN.
CONNOR: HI, MY NAME IS CONNOR,
AND I GO TO KAMIAH ELEMENTARY
SCHOOL IN KAMIAH, IDAHO.
MY QUESTION IS HOW MUCH FORCE
WOULD IT TAKE TO MOVE A 13-TON
TRAIN?
DEVINE: SO THE ANSWER TO THAT
ONE IS IT DEPENDS ON HOW YOU
WANT TO MOVE THE OBJECT.
AND SO IF YOU HAVE A 13-TON
OBJECT AND YOU JUST WANT TO MOVE
IT A LITTLE BIT, YOU DON'T WANT
TO SPEED IT UP, THEN IT'S NOT
GOING TO TAKE AS MUCH FORCE AS
IF YOU WANTED TO MAKE IT, SAY,
ACCELERATE AT THE RATE OF A
ROCKET SHIP OR SOMETHING.
SO IF YOU HAVE A LOT OF MASS AND
YOU WANT TO MAKE IT ACCELERATE,
THE AMOUNT OF FORCE YOU USE
DEPENDS ON THE ACCELERATION.
AND THAT'S NEWTON'S SECOND LAW,
FORCE EQUALS MASS TIMES
ACCELERATION.
IT DEPENDS ON THE MASS, BUT IT
ALSO DEPENDS ON THE
ACCELERATION, HOW MUCH YOU WANT
TO SPEED OR SLOW DOWN THAT
OBJECT.
GARDNER: THIS IS AN OPPORTUNITY
TO TALK ABOUT FRICTION, AS WELL.
SO A REALLY BIG, MASSIVE OBJECT
FLOATING IN SPACE NO MATTER HOW
LITTLE YOU PUSH ON IT, IT WILL
MOVE BECAUSE THERE'S NO OTHER
FORCES ACTING ON IT.
IF IT'S SITTING ON THE SURFACE
OF THE EARTH, YOU KNOW, WHETHER
IT'S ON A PARKING LOT OR ON A
ROAD, THERE'S A LOT OF FRICTION
BETWEEN -- AS WE TALKED ABOUT
EARLIER -- A LOT OF FRICTION
BETWEEN THAT BODY AND THE
SURFACE.
AND SO TO GET IT TO MOVE, YOU
HAVE TO OVERCOME THAT FRICTION
FORCE.
AND DEPENDING ON WHAT THOSE
SURFACES LOOK LIKE AND HOW BIG
THE OBJECT IS, THAT FRICTION
FORCE CAN BE BIGGER OR SMALLER.
BUT IT IS RELATED TO THE WEIGHT
OF THE OBJECT.
SO A 13-TON OBJECT IS GOING TO
HAVE A LOT OF FRICTION THAT YOU
HAVE TO OVERCOME BEFORE YOU CAN
GET IT TO MOVE.
NICOLE: HI, MY NAME IS NICOLE,
AND I GO TO OWYHEE-HARBOR
ELEMENTARY SCHOOL.
AND MY QUESTION IS HOW DO
ASTEROIDS MOVE THROUGH SPACE?
DEVINE: ASTEROIDS ARE REALLY
INTERESTING.
MOST OF THE ASTEROIDS IN OUR
SOLAR SYSTEM EXIST IN WHAT WE
CALL THE ASTEROID BELT, LOCATED
BETWEEN MARS AND JUPITER.
AND WE THINK THAT THOSE
ASTEROIDS ARE PROBABLY THE
START, THE BUILDING BLOCKS OF
PLANETS, FROM VERY EARLY IN OUR
SOLAR SYSTEM, THAT WERE WEREN'T
ABLE TO GROUP TOGETHER THROUGH
GRAVITY BECAUSE THEY WERE BEING
DISRUPTED BY JUPITER, THIS
REALLY BIG PLANET NEARBY WHOSE
GRAVITATIONAL FIELD WAS KEEPING
THOSE LITTLE POSSIBLE BUILDING
BLOCKS OF A PLANET FROM FORMING
TOGETHER UNDER GRAVITY.
THAT SAID, THOUGH, HOW DO THEY
MOVE, WELL, THEY ORBIT AROUND
THE SUN, JUST LIKE ANY OTHER
PLANET.
AND SO THEY'RE ORBITING AROUND
THE SUN.
THEIR ORBITS TEND TO BE MAYBE A
LITTLE BIT LESS CIRCULAR THAN
SOME OF THE PLANETS, AND SO
THERE ARE CERTAIN GROUPS OF
ASTEROIDS THAT HAVE ELLIPTICAL
ORBITS, WHICH MEANS MORE LIKE AN
OVAL THAN A CIRCLE.
AND THOSE ARE THE ONES THAT TEND
TO BE A LITTLE BIT MORE
INTERESTING TO US HERE ON EARTH,
BECAUSE IF THEY'RE MOVING RATHER
THAN IN A PERFECT CIRCLE, BUT IN
AN OVAL, THAT HAS A POTENTIAL,
THEN, FOR THEIR ORBIT
INTERSECTING OURS.
AND SO THOSE ARE THE ONES THAT
GET CLOSE ENOUGH THAT WE CAN
SOMETIMES SEE THEM CRASH INTO
OUR ATMOSPHERE, LIKE WE DID OF
COUPLE YEARS AGO IN RUSSIA,
WHERE IT CAUSED THAT BIG
EXPLOSION ABOVE A RUSSIAN TOWN.
AND SO GRAVITY KEEPS ASTEROIDS
IN AN ORBIT AROUND THE SUN, AND
THEY HAVE EITHER CIRCULAR ORBITS
OR OVAL ORBITS, AND IT'S THE
OVAL ONES THAT WE LIKE TO KEEP
AN EYE ON.
RUTH: HELLO, MY NAME IS RUTH,
AND I'M FROM BASIN ELEMENTARY.
THE QUESTION I WOULD LIKE TO ASK
YOU IS IF THERE'S NO GRAVITY IN
SPACE, CAN METEORS TRAVEL
FOREVER?
DEVINE: YES, METEORS COULD
TRAVEL FOREVER.
AND THIS IS GETTING BACK TO THE
IDEA THAT AN OBJECT IN MOTION,
LIKE A METEOR, WILL STAY IN
MOTION FOREVER AND EVER UNLESS
ACTED ON BY ANOTHER FORCE.
AND SO IF THERE WERE NO GRAVITY
AND NO OTHER FORCES, THEN THAT
METEOR WOULD CONTINUE TRAVELING
FOREVER.
IF THERE WAS NO GRAVITY AND IT
HIT SOMETHING, THEN THAT CONTACT
FORCE WOULD BE ENOUGH TO STOP
IT.
SO IF THERE WERE OTHER FORCES TO
BRING IT TO REST BESIDES
GRAVITY, THEN MAYBE IT WOULD
STOP.
BUT IF NO FORCES ACT ON IT,
THEN, YES, IT WOULD TRAVEL
FOREVER.
GARDNER: AND I THINK IT WOULD BE
IMPORTANT TO REALIZE THAT EVEN
IF THERE IS GRAVITY OUT THERE,
AND THERE IS, AN ASTEROID AS IT
NEARS ANOTHER MASS, ANOTHER
PLANET OR A STAR, IT COULD MOVE
ITS VELOCITY, BUT IT COULD KEEP
TRAVELING.
JUST BECAUSE IT'S EXPERIENCING
FORCE DOESN'T MEAN IT'S GOING TO
SLOW DOWN.
REMEMBER, A FORCE CAN SPEED UP
OR SLOW DOWN AND CAN ALSO CHANGE
DIRECTION.
AND SO WHAT, MORE THAN LIKELY,
HAPPENS WITH AN ASTEROID OUT IN
SPACE IS AS IT GETS NEAR A STAR,
IT'S SHIFTING A LITTLE BIT, BUT
IF IT'S TOO FAR AWAY, IT WON'T
GET CAUGHT INTO AN ORBIT; IT
WILL JUST MOVE INTO A DIFFERENT
DIRECTION ON TO THE NEXT STAR
AND SO ON.
SO IT COULD GO ON FOREVER EVEN
THOUGH IT'S BEING EXERTED, IT'S
BEING ACTED ON BY FORCES.
DANICA: HI, MY NAME IS DANICA,
AND
I COME FROM OWYHEE-HARBOR
ELEMENTARY SCHOOL.
AND MY QUESTION IS WHY DID YOU
DECIDE TO BECOME A SCIENTIST?
DEVINE: IT'S HARD TO REMEMBER
THE FIRST TIME THAT I REALIZED I
WANTED TO BE A SCIENTIST.
BUT I THINK IT WAS PRETTY EARLY
ON IN ELEMENTARY SCHOOL WHEN I
REALIZED THAT I JUST WAS
FASCINATED BY THE LESSONS I WAS
LEARNING IN SCIENCE, AND I
REALLY LIKED THAT SUBJECT AND
WANTED TO KEEP DOING IT.
IT WAS KIND OF MY FAVORITE PART
OF THE DAY.
AND THEN BY THE TIME I GOT ON TO
HIGH SCHOOL, I JUST STILL REALLY
ENJOYED THOSE CLASSES AND REALLY
ENJOYED THE STUFF I WAS LEARNING
THERE.
AND SO IT JUST KIND OF BUILT ON
AND KEPT GOING, AND I KEPT
ENJOYING IT, AND IT NEVER
STOPPED.
SO HERE I AM, A SCIENTIST.
GARDNER: AND I'LL ANSWER THAT
QUESTION BY CHANGING IT A LITTLE
BIT.
I'M NOT A SCIENTIST; I'M AN
ENGINEER.
BUT I AM A RESEARCHER.
AND SCIENTISTS AND ENGINEERS ARE
VERY SIMILAR TO EACH OTHER, THEY
HAVE VERY SIMILAR BACKGROUNDS,
BUT THEY HAVE DIFFERENT --
USUALLY DIFFERENT GOALS,
DIFFERENT REASONS TO GO INTO THE
FIELD.
I'VE ALWAYS BEEN INTERESTED IN
HOW THINGS WORK, AND USUALLY
MACHINES.
I'VE TAKEN THINGS APART A LOT
AND PUT THEM BACK TOGETHER
SOMETIMES.
AND I'M INTERESTED IN MAKING NEW
THINGS.
AND SO THAT'S WHY I WANTED TO BE
AN ENGINEER.
CARTAN-HANSEN: I'M SORRY, WE'VE
RUN OUT OF TIME.
MY THANKS TO JOHN AND KATHRYN
FOR ANSWERING STUDENTS'
QUESTIONS.
DEVINE: THANK YOU FOR HAVING US.
I HAD A LOT OF FUN.
GARDNER: THANK YOU.
CARTAN-HANSEN: AND MY THANKS TO
THE FOLKS HERE AT THE DISCOVERY
CENTER OF IDAHO FOR HOSTING US.
IF YOU WANT TO LEARN MORE, CHECK
OUT THE FORCE AND MOTION AREA ON
THE SCIENCE TREK WEBSITE.
YOU'LL FIND FACTS, LINKS, GAMES,
OUR FORCE AND MOTION BROADCAST
SHOW, AND LOTS MORE.
AND EVERY WEEK CHECK OUT MY BLOG
FOR THE LATEST SCIENCE NEWS FOR
KIDS.
ALL AT IDAHOPTV.ORG.
THANKS FOR JOINING US FOR
SCIENCE TREK: THE WEB SHOW .
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