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>> HELLO, MY NAME
IS SHANE KIMBROUGH,
AND I'M AN ASTRONAUT
LIVING AND WORKING ABOARD
THE INTERNATIONAL SPACE STATION.
WE'RE CURRENTLY ORBITING
250 MILES ABOVE
THE EARTH'S SURFACE
AT APPROXIMATELY
17,500 MILES PER HOUR.
YOU MAY BE WONDERING
HOW IT'S POSSIBLE
FOR THE SPACE STATION TO BE
CONTINUOUSLY ORBITING EARTH.
WELL, TODAY, WE'RE GOING TO
ANSWER THAT QUESTION
AND EXPLORE CENTRIPETAL FORCE
IN THE MICROGRAVITY ENVIRONMENT
OF THE SPACE STATION.
LET'S GET STARTED.
BEFORE WE DIVE INTO
CENTRIPETAL FORCE,
IT'S IMPORTANT TO LOOK
AT NEWTON'S FIRST LAW OF MOTION,
WHICH STATES THAT AN OBJECT
WILL CONTINUE MOVING
WITH A CONSTANT VELOCITY
ALONG A STRAIGHT PATH
UNLESS ACTED UPON
BY A NET EXTERNAL FORCE.
THIS MEANS THAT
THE SPACE STATION WILL
MOVE ALONG A STRAIGHT PATH
IF IT WEREN'T FOR ONE KEY
EXTERNAL FORCE ACTING ON IT--
EARTH'S GRAVITATIONAL PULL.
ANOTHER NAME
FOR THIS EXTERNAL FORCE
IS CENTRIPETAL FORCE.
A CENTRIPETAL FORCE
IS ANY NET FORCE
THAT KEEPS AN OBJECT MOVING
ALONG A CIRCULAR PATH.
GRAVITY, IN THIS CASE,
IS A CENTRIPETAL FORCE
BECAUSE IT IS THE FORCE
THAT IS KEEPING
OUR SPACE STATION MOVING
IN ITS CIRCULAR PATH
AROUND EARTH.
ALL RIGHT, HERE'S OUR EXAMPLE.
WE HAVE AKI HERE THAT HAS
AN OBJECT TIED TO A STRING.
IT'S JUST A YO-YO,
BUT IT'S AN OBJECT
ON THE END OF A STRING.
HE'S GONNA WHIRL
THIS OBJECT AROUND,
ATTACHED TO THE STRING
SO THAT IT'S MOVING
IN A CIRCULAR PATH.
THE STRING IN THIS DEMONSTRATION
PROVIDES A FORCE OF TENSION
WHICH IS THE CENTRIPETAL FORCE
KEEPING THE YO-YO REVOLVING
AROUND AKI'S HAND.
IT'S IMPORTANT TO NOTE
THAT CENTRIPETAL MEANS
"CENTER SEEKING."
THEREFORE A CENTRIPETAL FORCE
IS A CENTER-SEEKING FORCE.
CENTRIPETAL FORCE IS ALWAYS
DIRECTED INWARD,
TOWARD THE CENTER
OR AXIS OF REVOLUTION.
THIS IS BECAUSE IT'S
THE FORCE OF TENSION
FROM THE STRING PULLING INWARD
THAT KEEPS THE YO-YO
REVOLVING AROUND
THE AXIS OF REVOLUTION.
NOW AKI'S GOING TO SET
THE OBJECT MOVING
IN A CIRCULAR PATH FREE
AND REMOVE THAT CENTRIPETAL
FORCE BY RELEASING THE STRING.
AS YOU SAW,
ONCE THE TENSION FROM THE STRING
OR CENTRIPETAL FORCE
WAS REMOVED...
>> SLOW-MO VIEW.
>> THE OBJECT CONTINUES
TO FOLLOW NEWTON'S
FIRST LAW OF MOTION.
IT KEEPS MOVING
AT A CONSTANT VELOCITY
ALONG A STRAIGHT PATH
RELATIVE TO THE SPACE STATION.
CAN YOU THINK OF OTHER EXAMPLES
OF CENTRIPETAL FORCES
BACK ON EARTH?
TO LEARN MORE
ABOUT CENTRIPETAL FORCE,
USE THE CORRESPONDING
CLASSROOM CONNECTION
TO CONDUCT YOUR OWN EXPERIMENTS
AND DISCOVER OTHER WAYS
CENTRIPETAL FORCES PLAY OUT
IN YOUR EVERYDAY LIFE.
THANKS FOR EXPLORING
SOME PHYSICS WITH ME TODAY.
SEE YOU AGAIN SOON.