1. Chapter Forces

2. force – a ____ or ____ on an object
causes _____ or causes a moving object ________ or change _______
if a force acts on an object the object moves in the _________ of that force

3. force – any push or pull forces differ because of __________
example – baseball thrown by MLB pitcher and ball thrown by little girl
forces differ because of _______
example – baseball and softball
______, _____ and ________ are all related

4. all forces in nature come from the four elementary forces
______ _____force – holds atoms nucleus together
___________ force – like charges repel, opposite charges attract
_______ force – force that causes radioactive decay
________ – force of attraction that causes all masses to attract to one another
- electromagnetic and gravity most observed in our world

5. pound(___ or __) – English unit of force
newton(__) – SI unit of force
1 N = force added to ______object that accelerates the object by _______
1 lb = _______ N
150 lb person = N

6. how forces act
________forces – objects need to be in direct contact with one another
________
________, air resistance
________force
“__-__-_______” forces – objects are not touching or connected
_________
__________
___________

7. ________– force caused by gravitational field
_______– force of gravity on an object
______N on Earth
depends on ______and ________
a 10-kg rock weighs 98 N on Earth but only 16 N on the Moon
weighs 6x less because there is 6x less gravity on the moon

8. 5.2 Friction
_______– the force that opposes sliding motion of two touching surfaces
dependent on two factors
the _____of _______
bumps between the two surfaces catch or form ‘____________’
all surfaces are rough on the micro-scale
the _______pressing the surfaces together
more force pushing the two objects together = stronger microwelds

9. _____friction – friction between two objects that are not moving relative to one another

10. ________friction – force that opposes the motion of two surfaces sliding past one another.
caused by ________continually breaking and forming again
usually _____ than static friction
a force must be continually supplied to overcome sliding friction

11. _______friction – the force between a rolling object and the surface it rolls on
the force that opposes the motion of a rolling object
the wheel, surface or both are _____ where they are in contact
______ friction acts on the deformed area

12. ___ resistance – friction like force that opposes the motion of an object as it moves through air
causes objects to fall at different speeds
acts in the opposite direction of the objects motion
factors that affect air resistance
____ of the object
_____ of the object
_____ of the object is not a factor

13. reducing friction
_________
keeps two sliding surfaces from touching

14. _____ ______
changes sliding friction to rolling motion

15. _________levitation
separate sliding surfaces with magnets
supported on a cushion of air

16. Using friction
brakes
tires – groves increase friction when road is wet
nails
cleats or spiked shoes

17. friction changes NRG by wearing away moving objects
friction & NRG
friction changes NRG of _______into _____ NRG
rub you hands together
friction changes NRG by wearing away moving objects
engines wear out
tires go bald
rocks become rounded and smooth

18. 5.3 Forces & Equilibrium
_____ force – sum of 2 or more forces acting on an object

19. _______ forces – forces on an object that are equal in size and opposite in direction
net force = 0 = no motion

20. ________ – all forces cancel out leaving a zero net force
no motion

21. _______ forces – 2 or more forces on an object that are not equal in size
net force – object moves in direction of greater force

22. _______ forces _______ force – aka support force
force that acts “perpendicular” to the surface an object is pushing on it
table exerts a normal force on the book it is holding up
______ in strength to the force pushing the object in to the surface
table exerts an equal force to the weight of the book