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NEWTONS THIRD LAW OF MOTION. ACTION AND REACTION. NEWTONS THIRD LAW STATES THAT WHEN ONE OBJECTS EXERTS A FORCE ON ANOTHER OBJECT, THE OTHER OBJECT EXERTS A FORCE OF EQUAL AND OPPOSITE STRENGTH ON THE FIRST OBJECT. THIS MEANS…. FOR EVERY ACTION, THERE IS AN EQUAL AND OPPOSITE REACTION.
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ACTION AND REACTION • NEWTONS THIRD LAW STATES THAT WHEN ONE OBJECTS EXERTS A FORCE ON ANOTHER OBJECT, THE OTHER OBJECT EXERTS A FORCE OF EQUAL AND OPPOSITE STRENGTH ON THE FIRST OBJECT.
THIS MEANS… • FOR EVERY ACTION, THERE IS AN EQUAL AND OPPOSITE REACTION.
FOR INSTANCE, • THINK ABOUT SWIMMING AND DIVING. • TO DIVE OFF OF A DIVING BOARD OR POOL SIDE, YOU MUST EXERT A FORCE ONTO THE DIVING BOARD, WHICH THEN EXERTS A FORCE BACK ONTO YOU. • THIS IS WHAT ALLOWS YOU TO DIVE INTO THE WATER.
WHEN YOU SWIM, • YOU MAY KICK OFF OF A POOL WALL TO GET GOING OR AFTER A TURN. • WHEN YOU DO THIS, YOU ARE EXERTING A FORCE ONTO THAT WALL AND THE WALL IS EXERTING AN EQUAL AND OPPOSITE FORCE ONTO YOU.
MASS PLAYS AN IMPORTANT ROLL • SOMETIMES THE REACTION FORCE IS NOT OPPOSITE. • THIS OCCURS BECAUSE THERE ARE LARGE MASS DIFFERENCES. • AN EXAMPLE IS WHEN TWO ICE SKATERS PUSH OFF OF EACH OTHER.
THE ICE SKATERS • HAVE VARIOUS MASSES. • THEREFORE, WHEN THEY PUSH OFF OF EACH OTHER, THEY BOTH SHOW A REACTION.
THIS LAW IS EVERYWHERE! • SOME EXAMPLES ARE: • NEWTONS CRADLE. THIS IS THE PRIME EXAMPLE OF THIS LAW. • WALKING • PLAYING SOCCER • BALLOONS • CAR ENGINES
NEWTONS CRADLE • WHEN ONE BALL HITS THE OTHERS, ONE BALL ON THE OTHER END IS PUSHED OUT. • WHEN TWO BALLS HIT THE OTHERS, TWO BALLS ON THE OTHER END ARE PUSHED OUT. • WHEN THREE BALLS HIT THE OTHERS, THREE BALLS ON THE OTHER END ARE PUSHED OUT.
WHEN YOU WALK • YOU PUSH AGAINST THE GROUND AND THE GROUND PUSHES BACK AGAINS YOU.
WHEN YOU KICK A SOCCER BALL • THE BALL HAS AN EQUAL AND OPPOSITE REACTION OFF OF YOUR FOOT. • THE BALL MOVES AWAY FROM YOU (OPPOSITE) AND MOVES AT AN EQUAL STRENTH THAT YOU KICK IT (YOU KICK HARD, IT TRAVELS HARD)
WHEN YOU BLOW UP A BALLOON • AND LET IT GO THE BALLOON MOVES AROUND THE ROOM AS THE GAS IS EXPELLED. • THE ACTION IS THE GAS BEING RELEASED, THE REACTION IS THE BALLOON MOVING AROUND THE ROOM.
ACTION AND REACTION • FORCES DO NOT CANCEL EACH OTHER OUT EVEN THOUGH THEY ARE EQUAL AND OPPOSITE. • THIS IS BECAUSE THEY ARE ACTING ON DIFFERENT OBJECTS.
MOMENTUM • IS THE PRODUCT OF MASS AND VELOCITY. • THE MORE MASS AN OBJECT HAS, THE MORE MOMENTUM IT CAN OBTAIN AT VARIOUS VELOCITIES. • MOMENTUM = MASS X VELOCITY • MASS MUST BE IN KG AND VELOCITY IN M/S
EXAMPLE: • THAT’S WHY IT IS MORE DAMAGING FOR A FULL SIZED TANK TO HIT A HOUSE THAN FOR A TOY CAR TANK TO HIT A HOUSE. • EVEN IF THEY ARE TRAVELING AT THE SAME VELOCITY.
TO ACHIEVE HIGH MOMENTUM • YOU NEED EITHER A VERY HIGH VELOCITY OR A VERY BIG MASS. • BECAUSE OF THIS, EVEN SMALL OBJECTS CAN HAVE HIGH MOMENTUMS. • THINK OF BULLETS. THEY ARE VERY SMALL, BUT MOVE AT SUCH A HIGH VELOCITY THAT THEY GAIN GREAT AMOUNTS OF MOMENTUM.
CONSERVATION OF MOMENTUM • STATES THAT TOTAL MOMENTUM WILL NOT INCREASE OR DECREASE WHEN TWO OBJECTS COLLIDE. • SIMPLY, MOMENTUM WILL BE TRASFERED. • UNLESS AN OUTSIDE FORCE (LIKE FRICTION) ACTS UPON THOSE OBJECTS.
EXAMPLE • CAR B HITS CAR A FROM BEHIND. • NO BRAKES ARE APPLIED. • CAR A GAINS MOMENTUM, WHILE CAR B LOOSES MOMENTUM. • ESSENTIALLY, CAR B GIVES CAR A PART OF IT’S MOMENTUM. A B
SO IF • CAR A WAS TRAVELING WITH 5KG*M/S OF MOMENTUM AND CAR B WAS TRAVELING WITH 10KG*M/S OF MOMENTUMTHEN TOGETHER THEY WERE TRAVELING WITH 15KG*M/S OF MOMENTUM. A B 5KG*M/S + 10KG*M/S = 15KG*M/S
WHEN THEY HIT • CAR B TRANSFERRED OR GAVE 5KG*M/S OF MOMENTUM TO CAR A. • THIS MEANS THAT CAR A NOW HAS 10KG*M/S OF MOMENTUM AND CAR B NOW HAS 5KG*M/S OF MOMENTUM. • TOGETHER THEY STILL HAVE 15KG*M/S OF MOMENTUM. A B 10KG*M/S + 5KG*M/S = 15 KG*M/S
NOTICE • MOMENTUM WAS NEITHER CREATED NOR DESTROYED, BUT WAS MERELY TRASNFERED FROM ONE OBJECT TO ANOTHER.
