Simple Machines part 2

Machines The Simple Machines Lever Pulley Wheel & Axle Inclined Plane Screw Wedge

Objectives Identify six types of simple machines. Calculate ideal mechanical advantage. CLE 3202.4.3 Demonstrate the relationship among work, power, and machines.

A. Inclined Planes 1. A sloping surface, such as a ramp that reduces the amount of force required to do work, is an inclined plane.

A. Inclined Plane You can cover more distance but use less force. IMA = length of slope (effort distance) divided height of slope (resistance distance). Less force is required if a ramp is longer and less steep. By pushing a box up an inclined plane, the input force is exerted over a longer distance compared to lifting the box straight up.

E. Inclined Plane Inclined Plane sloping surface used to raise objects h l

Inclined Plane

B. The Screw A screw is an inclined plane wrapped in a spiral around a cylindrical post. You apply the input force by turning the screw. 3. The output force is exerted along the threads of the screw.

B. Screw

B. Screw Screw 4 . The IMA of a screw is related to the spacing of the threads. The IMA is larger if the threads are closer together.

Screw

C. Wedge Wedge – Chisels, knives, axes 1. A moving inclined plane with 1 or 2 sloping sides

Simple Machines 3 The Wedge The wedge is also a simple machine where the inclined plane moves through an object or material. 3. It changes the direction of the input force.

Wedge The red outlined area is an example of a wedge (chisels, knives, axes)

C. Wedge Zipper 2 lower wedges push teeth together 1 upper wedge pushes teeth apart

D. Compound Machines Compound Machine Combination of 2 or more simple machines

Examples: ax = wedge + lever; bicycle = pulley + wheel and axle + lever

A. Compound Machines Rube Goldberg Machine Rube Goldberg walks in his sleep, strolls through a cactus field in his bare feet, and screams out an idea for self-operating napkin: As you raise spoon of soup (A) to your mouth it pulls string (B), thereby jerking ladle (C) which throws cracker (D) past parrot (E). Parrot jumps after cracker and perch (F) tilts, upsetting seeds (G) into pail (H). Extra weight in pail pulls cord (I), which opens and lights automatic cigar lighter (J), setting off sky-rocket (K) which causes sickle (L) to cut string (M) and allow pendulum with attached napkin to swing back and forth thereby wiping off your chin. After the meal, substitute a harmonica for the napkin and you'll be able to entertain the guests with a little music.

Problems h Fe l MA Fr Fe = ? IMA = l ÷ h IMA = (3 m)÷(1.2 m) How much force must be exerted to push a 450 N box up a ramp that is 3 m long and 1.2 m high? IMA l h MA Fr Fe GIVEN: Fe = ? Fr = 450 N l = 3 m h = 1.2 m WORK: IMA = l ÷ h IMA = (3 m)÷(1.2 m) IMA = 2.5 Fe = Fr ÷ MA Fe = (450 N)÷(2.5) Fe = 180 N

Question: What are the two basic machines, and what other machines can they be modified to become? Answer: Lever – modified into pulley, wheel and axle; Inclined plane – modified into screw and wedge.

http://www.edheads.org/activities/simple-machines/index.shtml http://www.mos.org/sln/Leonardo/LeosMysteriousMachinery.html

Objectives Identify the types of levers and pulleys. Calculate ideal mechanical advantage. CLE 3202.4.3 Demonstrate the relationship among work, power, and machines.