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Ms. Wickersham. Concepts o All mechanical devices that humans use are made from six basic building blocks called simple machines. o It's important to.

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Presentation on theme: "Ms. Wickersham. Concepts o All mechanical devices that humans use are made from six basic building blocks called simple machines. o It's important to."— Presentation transcript:

1 Ms. Wickersham

2 Concepts o All mechanical devices that humans use are made from six basic building blocks called simple machines. o It's important to note that when a simple machine is used the same amount of work is require. o A SM reduces the amount of effort needed to move an object, but it results in moving it a greater distance to accomplish the same amount of work. o All complex mechanisms are made from simple machines.

3 Simple Machines Simple Machines: A simple device that provides a mechanical advantage, such as a wheel & axle, lever, pulley, or inclined plane. Compound Machines: A system of two or more simple machines (the game mouse trap is a great example).

4 LEVER AND FULCRUM PULLEY WHEEL AND AXLE INCLINED PLANE WEDGE (Modification of Inclined plane) SCREWS (Modification of Inclined plane) THERE ARE SIX SIMPLE MACHINES

5 Machines do work for us. What is Work? In order for work to be done, two conditions must be met: o a force must move an object some distance o and the force and distance the object moves must also be in the same direction. Therefore, if the object does not move, no work is being done.

6 Formula for Work In order to calculate work you need to have the measurement for Force and Distance. W=F x D W = Force (Newtons) x distance (meters) W = Force (lbs) x distance (feet)

7 How do machines help us do work? Mechanical advantage (MA) is the factor by which a mechanism multiplies the force put into it, making work easier. Machines provide us with MA in the following ways: o A machine can increase the force o A machine can change the direction o A machine can increase the speed

8 LEVER AND FULCRUM o A simple machine consisting of a rigid bar and a fulcrum (pivot point). o There are three classes: o 1 st class o 2 nd class o 3 rd class o s2KfO_yrPA s2KfO_yrPA

9 Three classes of Levers o The class of lever is determined by what is located in the middle. o Use this diagram to help you remember. o 1st class - fulcrum (pivot point) is in the middle o 2nd class - resistance (load) is in the middle o 3rd class - effort (force) is in the middle

10 FIRST CLASS LEVER 1 st class-the fulcrum is between the effort and the Load. The closer the load is to the fulcrum, the less effort needed to lift the load.

11 SECOND CLASS LEVER 2 nd class- the LOAD is between the effort and the fulcrum.

12 THIRD CLASS LEVER o These levers are used least often because their MA is less than 1. o This means the force needed to use them is greater than the force they can move. 3 rd class- the EFFORT is between the Load and the Fulcrum

13 How to calculate MA for levers: Can be calculated in two ways: If you know the distance MA = Effort Arm Resistance Arm (distance between the fulcrum and the input force) If you know the weight MA = Load/Resistance Effort

14 PULLEY o Pulley: A simple machine consisting essentially of a wheel with a grooved rim in which a pulled rope or chain can run to change the direction of the pull and thereby lift a load. o M58 M58

15 Pulley Systems There are three types of pulley systems: 1. A FIXED PULLEY 2. A MOVABLE PULLEY and 3. A COMBINATION PULLEY To calculate MA, you count the # of wheels or ropes, excluding the effort rope.

16 FIXED PULLEY A fixed pulley is “fixed” to something such as a ceiling, it cannot move. Work: changes the direction of the force A fixed pulley doesn't reduce the effort. MA = 0

17 MOVABLE PULLEYS A movable pulley is “movable” either vertically or horizontally. Work: changes the direction of the force MA = A movable pulley provides a mechanical advantage of 1.

18 COMBINATION PULLEY A combined pulley is a combination of the fixed and movable, sometimes called a block and tackle. Work: changes the direction of the force MA = weight/# of pulleys

19 WHEEL AND AXLE Wheel and Axle: a simple machine consisting of two concentric wheels. Work: Increases the speed and changes direction MA = wheel diameter/axle dia. =XlZYPFDjTJM =XlZYPFDjTJM

20 INCLINED PLANE Inclined plane: A simple machine used to raise or lower a load by rolling or sliding it instead of lifting it vertically. Work: Increases the force MA = Slope / height atch?v=pG_kT565-XQ atch?v=pG_kT565-XQ

21 WEDGES o A piece of material, such as metal or wood, thick at one edge and tapered to a thin edge at the other o The wedge is an inclined plane. o MA = side length/thickness

22 o The screw is an incline plane that is wrapped around a central axis. o The distance between the ridges is called the pitch (the distance advanced in a single turn). o MA = dia. of screw/lead of screw

23 Mechanical Advantage PL4S_gOG2-Y-hmAZqrMBtD5bqFcP3rBmkp&feature=results_main PL4S_gOG2-Y-hmAZqrMBtD5bqFcP3rBmkp&feature=results_main


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