Simple MachinesChapter 12 Section 3

1. There are six basic kinds of simple machines:

a. INCLINED PLANE d. LEVER

b. WEDGE e. WHEEL AND AXLE

c. SCREW f. PULLEY

Inclined plane Definition: Flat, sloped surface How it works: exert your input force over a

longer distance Mechanical Advantage: Ideal MA = Length

of incline/height of incline Example: ramp

Wedge Definition: A DEVICE THAT IS THICK AT

ONE END AND TAPERS TO A THIN EDGE AT THE OTHER END

How it works: YOU MOVE THE INCLINED PLANE ITSELF

Mechanical Advantage: LENGTH OF THE WEDGE/WIDTH OF THE WEDGE

Example: Ax

Screws Definition: AN INCLINED PLANE WRAPPED

AROUND A CYLINDER How it works: EXERT INPUT FORCE ON THE

SCREW AS YOU TWIST, THREADS INCREASE THE DISTANCE OF THE INPUT FORCE

Mechanical Advantage: LENGTH AROUND THE TREADS/LENGTH OF THE SCREW

Example: Screw

Levers Definition: RIGID BAR THAT IS FREE TO PIVOT,

OR ROTATE, ON A FIXED POINT How it works: EXERT INPUT FORCE, PIVOTS

ON FULCRUM, EXERTS OUTPUT FORCE Mechanical Advantage: DISTANCE FROM

FUCLCRUM TO INPUT FORCE/DISTANCE FROM FULCRUM TO OUTPUT FORCE

Example: Seesaw

Wheel and axle Definition: SIMPLE MACHINE MADE OF TWO

CIRCULAR OR CYLINDRICAL OBJECTS FASTENED TOGETHER THAT ROTATE ABOUT A COMMON AXIS

How it works: APPLY INPUT FORCE TO TURN THE WHEEL. AXLE ROTATES AND EXERTS A LARGE OUTPUT FORCE – INCREASES THE FORCE

Mechanical Advantage: RADIUS OF WHEEL/RADIUS OF AXLE

Example: screwdriver

Pulley Definition: A SIMPLE MACHINE MADE OF A

GROOVED WHEEL WITH A ROPE OR CABLE WRAPPED AROUND IT

How it works: PULLING ON ONE END OF A ROPE, INPUT FORCE- OUTPUT FORCE PULLS ON AN OBJECT ON THE OTHER END OF THE ROPE

Mechanical Advantage: NUMBER OF SECTIONS OF ROPE THAT SUPPORT THE OBJECT

Example: Flagpole

3. The three classes of levers differ in the positions of the FULCRUM, INPUT FORCE and OUTPUT FORCE.

4. First class levers: Change the direction of the INPUT FORCE.

a. Fulcrum is closer to output force, levers INCREASE force

b. Fulcrum is closer to the INPUT force, increase distance

c. Examples: SCISSORS PLIERS SEESAW

d. Draw 1st class lever p. 427. Label fulcrum, output force and input force

Output force Input Force Fulcrum

5. Second class lever: Increase force, but do not change the DIRECTION of the input force.e. Examples: DOORS NUTCRACKERS

BOTTLE OPENERSf. Draw 2nd class lever p. 427: Label Input force,

Output force and fulcrumINPUT FORCE OUTPUT FORCE FULCRUM

6. Third class levers: Increase DISTANCE but do not change the DIRECTION of the input force.

a. examples FISHING POLES SHOVELS BASEBALL BATS

b. Draw example with fulcrum, input force and output force

input force output force

fulcrum

7. Types of Pulleys: Draw an example of each in the margin

a. A FIXED pulley does not change the amount of force applied. It will change the DIRECTION of the force.

b. A movable pulley DECREASES the amount of input force needed. It does not change the DIRECTION of the force.

c. A block and TACKLE is a pulley system made up of FIXED and MOVABLE pulleys.

8. Most of the machines in your BODY are levers that consist of bone and muscles.

9. In your body, what is the Lever? TENDONS AND MUSCLE PULLING ON BONE Fulcrum? JOINT NEAR THE TENDON ATTACHED TO THE BONE Input force? MUCLES Output force? USED FOR DOING WORK, EX: LIFTING HAND

10. Where is the wedge in your body? INCISORS (TEETH)

11. What is a compound machine? A MACHINE THAT UTILIZES TWO OR MORE SIMPLE MACHINES

12. The ideal mechanical advantage of a compound machine is the PRODUCT of the individual ideal mechanical advantage of the SIMPLE machines that make it up.

13. What is an example of a compound machine? APPLE PEELER

14. What simple machines make up this machine? HANDLE – WHEEL AND AXLE; AXLE – SCREW THAT TURNS; WEDGE – PEELS THE SKIN; LEVER – HOLDS THE MACHINE IN PLACE (ENGAGES A SUCTION CUP)