Download Chapter 19- Newton*s First Law

CHAPTER 19NEWTON’S FIRST LAW
8TH GRADE
INTRODUCTION
PGS. 550-552
DO NOW…
• WRITE AGREE OR DISAGREE FOR THE FOLLOWING STATEMENTS.
Agree or
Disagree
Statement
A force is a push or pull.
Objects must be touching each other to apply forces
on one another.
Gravity pulls on all objects that have mass.
An object traveling in a circle at a constant speed is
not accelerating.
OBJECTIVES
STUDENTS WILL…
• DISTINGUISH BETWEEN BALANCED AND NET FORCES
• DESCRIBE NEWTON’S FIRST LAW OF MOTION
FORCES ON A BOOK
• IF A BOOK WERE PUSHED ACROSS A TABLE….
• WHAT IS THE MOTION OF THE BOOK?
• IN THIS CHAPTER, YOU WILL LEARN TO DESCRIBE THE
MOTION OF THE BOOK IN TERMS OF THE FORCES
ACTING UPON IT AND ACCORDING TO NEWTON’S FIRST
LAW OF MOTION.
HAVE YOU EVER THOUGHT….?
• AN OBJECT AT REST RESISTS ACCELERATION ONLY BECAUSE
OF FRICTION. TRUE OR FALSE?
• HAS ANYONE EVER HELPED TO PUSH A STALLED CAR?
• DID YOU NOTICE THAT IT TAKES A LOT OF EFFORT TO GET
THE CAR GOING AND LESS EFFORT TO KEEP IT GOING?
• WHY DOES IT TAKE A LARGER FORCE TO MOVE A STOPPED
CAR THAN IT DOES IT PUSH A MOVING CAR?
FORCE
• A FORCE IS A PUSH OR PULL.
• EXAMPLES: GOLF CLUB ON A GOLF BALL, THE MAGNET ON A CRANE
PULLING PIECES OF SCRAP METAL UPWARD
• WHAT IS FORCE?
• WHAT FORCES ARE ACTING ON YOU?
COMBINING FORCES
• MORE THAN ONE FORCE AN ACT ON AN OBJECT AT THE SAME TIME
AND THE COMBINATION OF THESE FORCES ACTING ON AN OBJECT IS
THE NET FORCE.
HOW FORCES COMBINE TO FORM A NET FORCE
• 2 IMPORTANT THINGS TO REMEMBER
1) IF FORCES ACT IN THE SAME DIRECTION, THE
FORCES ADD TOGETHER.
2) IF THE FORCES ACT IN OPPOSITE DIRECTIONS, THE
NET FORCE IS THE DIFFERENCE BETWEEN THE
FORCES.
BALANCED AND UNBALANCED FORCES
• A FORCE CAN ACT ON AN OBJECT WITHOUT CAUSING IT TO ACCELERATE IF
OTHER FORCES CANCEL THE PUSH OR PULL OF THE FORCE.
BALANCED FORCES
- 2 OR MORE FORCES EXERTED ON AN OBJECT ARE BALANCED IF THEIR EFFECTS
CANCEL EACH OTHER AND THEY DO CHANGE THE OBJECT’S VELOCITY. IF THE
FORCES ARE BALANCED, THEN THE NET FORCE IS ZERO.
UNBALANCED FORCES
-IF THE NET FORCE IS NOT ZERO, THE FORCES ARE UNBALANCED. THEN THE EFFECTS
OF THE FORCES DON’T CANCEL AND THE OBJECT’S VELOCITY CHANGES.
NEWTON’S FIRST LAW OF MOTION
• WHAT CAN YOU TELL ME ABOUT SIR ISAAC NEWTON?
• SIR ISAAC NEWTON
NEWTON’S FIRST LAW OF MOTION
• STATES THAT IF AN OBJECT IS AT REST AND THE NET FORCE IS ZERO, IT WILL
STAY AT REST. IF IT IS ALREADY MOVING AND THE NET FORCE ON IT IS
ZERO, IT WILL CONTINUE TO MOVE IN A STRAIGHT LINE WITH A
CONSTANT SPEED.
• FIRST LAW OF MOTION
FOR REVIEW…
• WHAT IS THE DIFFERENCE BETWEEN A BALANCED AND
AN UNBALANCED FORCE?
FOR NEXT TIME…
• TEST SIGNED BY A PARENT DUE THURSDAY, 10/24
• READ PGS. 553-555 (PLEASE MAKE SURE YOU READ!)
• DEFINE NEWTON’S FIRST LAW OF MOTION AND
FRICTION.
TYPES OF FRICTION
8TH GRADE
MINI LAB-OBSERVING FRICTION
REVIEW AND PREVIEW…..
WITH YOUR LAB GROUP, ANSWER THE QUESTION ON
THE INDEX CARD. BE PREPARED TO SHARE YOUR
ANSWER WITH THE REST OF THE CLASS.
OBJECTIVES
STUDENTS WILL…
CREATE A FOLDABLE TO EXPLORE THE THREE DIFFERENT
TYPES OF FRICTION
COMPLETE A MINI LAB TO OBSERVE FRICTION IN ACTION
FRICTION FOLDABLE
• A DIFFERENT WAY OF TAKING NOTES AND ORGANIZING
INFORMATION
• SET UP FOLDABLE ACCORDING TO TEACHER INSTRUCTIONS
• HEADING: TYPES OF FRICTION AND DEFINITION OF FRICTION ON FLIP
SIDE
• THREE TABS FOR TYPES OF FRICTION—LABELED AS WE GO ALONG
• QUESTIONS/CONFUSION?
FRICTION AND NEWTON’S FIRST LAW
• FRICTION IS THE FORCE THAT BRINGS NEARLY EVERYTHING TO A
STOP. IT ACTS TO RESIST SLIDING BETWEEN TWO TOUCHING
SURFACES.
• HOW ARE FRICTION AND NEWTON’S FIRST LAW RELATED?
• NEWTON’S FIRST LAW STATES: IF THE NET FORCE ACTING ON AN
OBJECT IS ZERO, THE OBJECT REMAINS AT REST. IF THE OBJECT IS
ALREADY MOVING, IT CONTINUES TO MOVE IN A STRAIGHT LINE
WITH CONSTANT SPEED.
FRICTION AND NEWTON’S FIRST LAW
•FRICTION FOLLOWS NEWTON’S FIRST LAW.
(IT DOES NOT CHANGE IT!)
•IT ACTS UPON AN OBJECT IN MOTION
THEREFORE TRYING TO BRING IT TO A STOP.
•IT ALSO HELPS OBJECTS AT REST STAY AT REST.
TYPES OF FRICTION
STATIC FRICTION
• PREVENTS AN OBJECT FROM MOVING WHEN A FORCE IS
APPLIED TO IT
• THINK “STATIONARY OR STILL”
• EXAMPLES:
• A BACKPACK SITTING IN THE MIDDLE OF THE HALLWAY, A
VASE RESTING ON A TABLETOP
TYPES OF FRICTION
SLIDING FRICTION
• SLOWS DOWN A SLIDING OBJECT
• ACTS IN THE DIRECTION OPPOSITE OF A MOTION TO SLOW SOMETHING
DOWN
• THINK “SLOWING”
• EXAMPLES:
• A BASEBALL PLAYER SLIDING INTO HOME BASE, A CHAIR THAT WAS PUSHED
SLOWING DOWN AND STOPPING IN THE MIDDLE OF A ROOM
TYPES OF FRICTION
ROLLING FRICTION
• A FORCE THAT MAKES A CIRCULAR SHAPE/WHEEL TURN
• FRICTION BETWEEN THE ROLLING OBJECT AND THE SURFACE ON
WHICH IT IS ROLLING
• THINK “WHEELS”
• EXAMPLES:
• A SCOOTER MOVING DOWN THE STREET, A STROLLER BEING PUSHED
DOWN A SIDEWALK
EXAMPLES OF FRICTION
• WOODEN SURFACE
• 3 OBJECTS: SHOE, TOY WITH WHEELS, PIECE OF METAL
• PREDICT: WHICH OBJECT WILL SLIDE THE FASTEST/SLOWEST?
(WHY?)
• WHICH OBJECT WILL HAVE THE GREATEST/LEAST AMOUNT OF
FRICTION? (WHY?)
• OTHER EXAMPLES OF FRICTION IN THE CLASSROOM OR AROUND
THE SCHOOL.
MINI LAB: OBSERVING FRICTION
• PURPOSE: STUDENTS WILL OBSERVE THE STATIC AND
SLIDING FRICTION BETWEEN VARIOUS OBJECTS.
• LAB PROCEDURES/DIRECTIONS/SAFETY PRECAUTIONS
• COMPLETE LAB WORKSHEET—DON’T FORGET TO EXPLAIN
WHY!
FOR REVIEW…
• DEFINE AND IDENTIFY THE TYPE OF FRICTION IN EACH OF THE FOLLOWING
SITUATIONS.
• 1) A BICYCLE TIRE ROLLING ALONG THE ROAD
• 2) A BOX RESTING ON A RAMP
• 3) AN TEXTBOOK BEING PUSHED ACROSS A TABLE AND COMING TO A STOP
• FOR NEXT TIME…
• FINISH LAB WORKSHEET IF NEEDED
• READ PAGES 556-559
• DEFINE NEWTON’S SECOND LAW AND WEIGHT ON INDEX CARDS