Obj 3 forces that act on objects resulting in motion
1. Applications of forces
• Work: is done only when force applied to
an object actually moves the object.
Measured in joules (J).
• Force: is anything that causes a change in
motion. Measured in Newtons (N).
2. • Effort: Is the amount of force you apply to
get work done. Measured in kilograms
(kg).
• Distance: is the amount of space an object
moves. Measured in meters (m).
3. Work with a Machine
• WORK STAYS THE SAME!!!!
• Force is decreased. Less effort is applied.
It is easier for work to be done.
• Distance increases.
4. Without a machine
• WORK STAYS THE SAME!!!!
• Force increases. More effort is necessary.
It is harder for work to be done
• Distance decreases.
5. Levers
• A simple machine consisting of a bar that
pivots at a fixed point, called a fulcrum.
• There are three classes of levers
6. 1st Class
• The FULCRUM is always in between the
input force and the out put force.
• Mechanical Advantage: <1, =1, >1
• Examples: Crowbar, scissors, rowboat,
teeter totter.
7. 2nd Class
• The OUTPUT FORCE (LOAD) is always
between the fulcrum and the input force.
• Mechanical Advantage: >1 (greater than
one)
• Examples: Bottle opener, wheel barrow.
8. 3rd Class
• The INPUT FORCE is always between the
fulcrum and the output
force (load).
• Mechanical Advantage: <1
(less than one)
• Examples: Barbells, hammer
Fishing pole.
9. Types of Friction
• Static Friction: when a force is applied to
an object, but does not make it move
10. Types of Friction
• Sliding: it opposes the movement of
objects that are sliding.
11. Types of Friction
• Rolling: a force that opposes a rolling
object on another surface. It is less than
sliding friction, so it is easier to move
objects.
12. Types of Friction
• Fluid: it opposes motion of objects
traveling through a liquid or gas.
14. Changing Force and Motion
• Isaac Newton came up with three laws
that explain why objects move or don’t
move.
15. Changing Force and Motion
• 1st Law: an object at rest remains at rest
and an object in motion remains in motion
at a constant speed and in a straight line
unless acted on by an unbalanced force.
16. Changing Force and Motion
• 2nd Law: the acceleration of an object
depends on the mass of the object and the
amount of force applied.
• 3rd Law: whenever one object exerts a
force on a second object, the second object
exerts an equal and opposite force on the
first.
