Simple Machines and Mechanical Advantage SPS8E – IN 33 Physical Science Ms. Lockhart
What Are the Six Simple Machines? Screw Wedge Inclined Plane Pulley Wheel and Axle Lever
How Do Simple Machines Make Work Seem Easier? • Simple Machines just change • The direction of the force • The amount of force you exert • The distance that force has to travel
Work is Constant Machines make work SEEM easier but it is the same amount of WORK.
Although it takes less force for car A to get to the top of the ramp, all the cars do the same amount of work. A B C
Inclined Plane • Further distance, less effort.
Mechanical Advantage (MA) • MA = distance of ramp • height of ramp • = 15/3 = 5 • Work seems five times easier 15 m Din Dout 50 N 3 m Fin 10 N
Mechanical Advantage (MA) • MA = Output Force • Input Force • 50/10 = 5 • Work seems five times easier SAME ANSWER! Fout 15 m Din Dout 50 N 3 m Fin 10 N
MA-Wheel and Axle Small gears rotate faster than larger gears. Larger Gear Smaller Gear
How to Calculate the MA of a Wheel and Axle? • 2. The wheel of a small dirt bike has a radius of 30 cm. The axle has a radius of 20 cm. What is the mechanical advantage of the wheel and axle? • 5. The mechanical advantage of a steering wheel is 15. If the radius of the steering column (axle) is 5 cm, what is the radius of the steering wheel?
Essential Questions p. 23 (Answer questions 3 on page 22)
What is the MA of a Pulley? • MA • One Fixed pulley: • MA • Count # ropes supporting the pulley. Movable Pulley:
Choice • Students will have an opportunity to work on the mechanical advantage of simple machines by either: • Website – Find the MA of pulleys (slide 12) • Website – Test your knowledge of simple machines (slide 13) • Cooperative Groups – The manager will quiz you on identifying simple machines and mechanical advantage. (handouts)
Practice - Pulleys MA • http://www.dynamicscience.com.au/tester/solutions/hydraulicus/pulleys2.htm • Calculate the MA for each picture. Start with the first and then select ‘exercise’. When you get to the bottom, select ‘continue’. • First picture – 4 strings (MA 4) • Second picture – 4 strings (MA 4) • Third picture – 3 strings (MA 3) • Four picture – 4 strings (MA 4) • Fifth picture – 3 strings (MA 3) • Sixth picture – same • Seventh picture (wow!) – 6 strings (MA 6)
Activity – Label Simple Machines • Going further: Try this online activity! • http://www.teachengineering.org/collection/cub_/lessons/cub_simple/cub_simple_lesson01_worksheet.pdf • Answers • 5, 3, 6, 2, 1, 4 • Pulley (car has wheel and axle), Wheel and axle, Wheel and axle AND lever • Wedge, Lever, Screw • Incline plane, Incline plane, Wheel and axle • Lever, Lever, Pulley
The Lever • A bar with a fixed point (fulcrum).
Types of Levers MA = Input Arm Output Arm
First Class Lever EFR (1st Class) Fulcrum is in the middle area
First Class Lever - Examples Examples • Crowbars • Scissors • Pliers • Tin snips • Seesaws
Second ClassLever FRE (2nd Class) Fulcrum is at the end Your work is at the end (effort force)
Second Class Lever Examples • Nut crackers • Wheel barrows • Doors • Bottle openers
Third Class Lever FER (3rd Class) Fulcrum is on the end. Your work is in the middle area
Third Class Lever Examples • Tweezers • Arm hammers • Shovels
Practice - Choice • Cooperative Groups – secretaries will test your knowledge of simple machines, mechanical advantage and types of levers. • Study – read over your notes for p. 33. Write a summary of what you learned or what is most important and why. • EQ – complete the EQ for this topic (p. 22) – SPS8E #3 • Unpack the Standard – Unpack standard 8 (can be computer work) • Relearn – review the BrainPop videos on the topic.
BrainPop • Pulley - http://www.brainpop.com/technology/simplemachines/pulley/ • Levers - http://www.brainpop.com/technology/simplemachines/levers/ • Incline Plane – • http://www.brainpop.com/technology/simplemachines/inclinedplane/
Rube Goldberg Machines • Rube Goldberg machines are examples of complex machines. • All complex machines are made up of combinations of simple machines. • Rube Goldberg machines are usually a complicated combination of simple machines. • By studying the components of Rube Goldberg machines, we learn more about simple machines and energy transformations.
Rube Goldberg Machine Honda Commercial • http://www.teachertube.com/viewVideo.php?video_id=15955 Japanese Rube Goldberg • http://www.dailymotion.com/video/x14rj6_pitagora-suicchi-rube-goldberg-mach_fun