Presentation is loading. Please wait.

Presentation is loading. Please wait.

Mechanical Advantage What do simple machines do for us anyway?

Similar presentations


Presentation on theme: "Mechanical Advantage What do simple machines do for us anyway?"— Presentation transcript:

1 Mechanical Advantage What do simple machines do for us anyway?

2 There are four ways that a machine helps us to do work.  Transfers our effort force from one place to another. Ex: seesaw  Multiply your effort force. Ex: crowbar  Magnify speed and distance. Ex: baseball bat  Changing the direction of the force. Ex: pulley on the flagpole

3 There are 2 types of mechanical advantage.  IMA – Ideal mechanical advantage.  This is the number of times a machine is designed to multiply your effort force.  It is based on measurements of the machine.  Ignores friction  AMA – Actual mechanical advantage  This is the number of times the machine actually multiplies your effort force.  AMA = resistance force/effort force.  Includes the effects of friction IMA is always larger than AMA.

4 Mechanical Advantage  Definition - a quantity that measures how much a machine multiplies force or distance  Two types Actual: measures the actual forces action on amachine - AMA = output force input force Ideal: measures the mechanical advantage in the absence of friction - IMA = input distance output distance

5 Mechanical Advantage Problems Q: Alex pulls on the handle of a claw hammer with a force of 15 N. If the hammer has a actual mechanical advantage of 5.2, how much force is exerted on a nail in the claw? A: output force = (5.2)(15N) = 78 N Q: If you exert 100 N on a jack to lift a 10,000 N car, what would be the jack’s actual mechanical advantage (AMA) A: AMA= 10,000 N / 100 N = 100

6 Mechanical Advantage Problems Q: Calculate the ideal mechanical advantage (IMA) of a ramp that is 6.0 m long and 1.5 m high? A: IMA = 6.0m / 1.5m = 4.0 Q: The IMA of a simple machine is 2.5. If the output distance of the machine is 1.0 m, what is the input distance? A: Input distance = (2.5)(1.0m) = 2.5 m

7 Efficiency of Machines  Definition - a quantity, usually expressed as a percentage, that measures the ratio of useful work input  Formula - Efficiency = useful work output work input - % of work input that becomes work output - due to friction, efficiency of any machine is always less than 100%

8 Efficiency Problems Q: Alice and Jim calculate that they must do 1800 J of work to push a piano up a ramp. However, because they must also overcome friction, they must actually do 2400 J of work. What is the efficiency of the ramp? A: 1800 J/ 2400 J x 100 = 75% Q: If the machine has an efficiency of 40%, and you do 1000 J of work on the machine, what will be the work output of the machine? A: Work Output = (Efficiency x work input) / 100% Work Output = (40% x 1000 J) / 100% = 4.0 x 10 2 J

9 Simple Machines  Definition - one of the six basic types of machines  2 types or families 1. lever 2. inclined planes

10 Levers  Definition - a rigid bar that is free to move around a fixed point ex. screwdriver - all levers have a rigid arm that turns around a point called the fulcrum - force is transferred from one part of the arm to another - original input force can be multiplied or redirected into output force - levers are divided into 3 classes, based on the locations of the input force, output force, and the fulcrum

11 There are 3 Classes of Levers  Depends on the location of 3 items: 1. Fulcrum – fixed point on a lever 2. Effort Arm – the part of the lever that exerts the effort force. 3. Resistance Arm – the part of the lever that exerts the resistance force.  EA   RA 

12 1 st Class Lever Changes the direction of the force Multiplies effort force Magnifies speed and distance Ex: seesaw, crowbar, scissors

13 2 nd Class Lever Multiply effort force Mechanical advantage is always greater than 1. Ex: bottle opener, boat oars, wheel barrow

14 3 rd Class Lever Magnifies speed and distance Mechanical Advantage always less than 1 Ex: baseball bat, golf club, broom, shovel

15 Wheel and Axis Definition - simple machine that consists of two disks or cylinders, each one with a different radius ex. steering wheel, screwdriver - made of a level or a pulley (wheel) connected to a shaft (axle) - small input force, multiplied to become a large output force

16 Inclined Planes  Definition - slanted surface along which a force moves an object to a different elevation ex. knife, ax, zipper, wedge, screw - ramp redirects the force applied to lift object upward - turns a small input force into a large output force by spreading the work out over a large distance - wedge: functions as two inclined planes back to back, turning a downward force into two forces directed out to the sides -screw: an inclined plane wrapped around a cylinder

17 Pulleys Definition - a simple machine that consists of a rope that fits into a groove in a wheel. - very similar to a lever - point in the middle of the pulley is like a fulcrum - rest of the pulley acts like the rigid arm 3 Types of Pulleys - fixed pulleys - moveable pulleys - pulley system

18 Fixed And Movable

19 Pulley System

20 1. What is the IMA of this pulley system? 2. Ignoring friction, if you want to lift the resistance 3 meters what will the effort distance be? 3. Ignoring friction how much effort force will be necessary to lift a load of 15 newtons? 4. How much work is done?

21 Compound Machines  Definition - a machine that is made of more than one simple machine ex. scissors, jacks, bicycle, washing machine, car, clock


Download ppt "Mechanical Advantage What do simple machines do for us anyway?"

Similar presentations


Ads by Google