Motion & Forces
Chapter 3, Section 3
(Pages 81-86)
Force
_________________ or __________________ that one objects exerts on another
Has a _______________ and a ___________________
What would this make force?
A _______________________!
Direction is the direction the ______________________________________________________________
Example: when you lift your backpack you apply an _______________________ force
SI Unit: _____________________________
Force can cause the _______________________ of an object to ______________________
Example: A ball is coming at a tennis player – player swings the racket – causes the
ball to ______________________ and move in the ________________________ direction
Balanced Forces
Net Force:
Example: Two students are pushing on opposite sides of a box – both are pushing
with an ____________________ force, but in an ___________________ direction
Net force = _____________________
Balanced Forces:
Unbalanced Forces
Example: Two students are pushing with ____________________ forces in __________________
directions – net force occurs in the direction of the ________________ force - box will
__________________________
Unbalanced Forces:
Net force will be the _____________________________ between the two forces
Example: students push on box in _________________ direction – forces are
___________________ or added together
_____________________ does change
Friction
Causes:
All surfaces have __________________ & ___________________
When two surfaces are in contact, _________________ occurs where the bumps & dips
touch each other – ______________________ form
Microwelds tend to make the surfaces stick together and cause ________________________
to occur
Static Friction
Example: You push a heavy box, and it doesn’t move – another force has to be acting
in the _________________________ direction:
_____________________________________!
Sliding Friction
Example: You and a friend push together on the box and the box slides along the
floor – if you stop pushing, what happens?
The box ______________________ due to ______________________ friction!
Rolling Friction
When an object ________________ over a surface, a frictional force due to rolling friction
_________________ the object down
Rolling friction is _________________ than sliding friction
Reason why it is _________________ to move a heavy object if it is on wheels
Air Resistance
When objects fall toward Earth, it is pulled downward by _______________________
A ___________________________ called air resistance opposes the motion of objects that
move through the _______________________
Causes objects to fall with difference _______________________ and
____________________________
Acts in direction _______________________ to the velocity of an object
If an object is falling _____________________________, air resistance is pushing
______________________
Size of air resistance depends on the __________________ and __________________ of an
object
Air resistance, not _______________, is why feathers, leaves, and sheets of paper fall
more slowly than pennies, acorns, & apples
Terminal Velocity
As an object falls, _______________________ causes the object to _______________________
As the speed of a falling object ________________________, the upward force of air
resistance also ______________________________
Eventually the upward force of air resistance and the force of gravity
_________________________ out
Object will fall with a constant __________________ – ________________ Velocity