Simple machines and mechanisms Lesson 5.0 and 5.1 Pages

What to know ► 6 types of simple machines ► 3 classifications of levers ► Ideal mechanical advantage of simple machines: how to find them ► What a mechanism is

Six simple machines ► Lever ► Wheel and axel ► Incline plane (ramp) ► Screw ► Pulley ► Wedge

Terminology ► Mechanism: is made up of several different types of machines that work together to perform a specific function. ► Simple machine: is a machine that requires the application of a single force to do work.

Levers ► A lever is a simple machine that changes the amount of force you must exert in order to move an object. ► There are five components to a lever:  The fulcrum  The effort force  The load  The effort arm  The load arm

Parts of a lever Effort arm

Parts of a lever ► Fulcrum – supports the lever and is a fixed point. It is the point of rotation. ► Effort force – the force you exert on a lever ► The load – the mass of an object that is being moved. ► Effort arm – the distance between the fulcrum and the effort force ► Load arm – the distance between the fulcrum and the load.

► Class one:  Teeter totter  Scissors ► Class two:  Wheel barrel  Bottle opener ► Class three:  Rake  Hockey stick Class of levers

► First class: output force is always in the opposite direction of the input force. ► Second class: input and output forces are always in the same direction. ► Third class: input and output are in the same directions AND the mechanical advantage is always less than one.  They increase speed and distance.

Ideal Mechanical advantage of a lever ► Remember MA = output divided by input ► However, you need an experiment to find this out, so we often find the ideal mechanical advantage – assuming friction does not play a huge role. ► SO:  IMA = length of input arm/length of output arm

Lets try to figure it out. 1. If we have a lever and the input arm is 40cm and the length of the output arm is 10cm, what is the I.M.A.? 2. If the length of the load arm is 4cm and the length of the effort arm is 20cm, what is the I.M.A.?

Answers 1. Input arm / output arm = 40 / 10  Therefore the answer is 4.  The I.M.A. = 4 2. Input or effort arm/ output or load arm  20 / 4  The I.M.A. = 5

STOP ► At this point, lets stop and take notes on levers. ► Complete learning checkpoint questions 1-3 on page 135 ► Complete handout page 532.

Pulleys ► A pulley consists of a grooved wheel with a rope, cable or chain running around it. The pulley is free to rotate. ► A pulley can:  Change the direction of the force  Increase the output force depending upon: ► If it is a fixed or moveable pulley

Fixed v. Moveable ► A fixed pulley is attached to a stationary object and ONLY changes the direction of the force. It has a mechanical advantage of only one (1). ► A moveable pulley is allowed to move along a rope and increases the input force to get a mechanical advantage of 2  The load is often attached to the pulley.

I.M.A. of a pulley System ► The I.M.A. of a pulley system is equal to he number of support ropes.  See page 137 for pictures. ► By counting the support ropes, you’ll know the I.M.A. of the pulley system.

► The effort arm and load arm on pulley’s are the same. So how do you achieve Mechanical Advantage? ► When you combine fixed and moveable pulleys you get block and tackle and in the process, create Mechanical Advantage. ► A compound pulley is made up of several pulleys working together.

Wheel and Axle ► A wheel and axle consists of a shaft or axle that is attached to a larger disk, called the wheel.  Examples: doorknobs, bike pedals, screwdriver

I.M.A. of a wheel ► If you turn the axle:  IMA = radius of axle / radius of wheel ► If you turn the wheel:  IMA = radius of wheel / radius of axle

Inclined Planes ► An incline plane (ramp) is a sloping surface on which an object can move. ► It decreases or reduces force but increases distance.

IMA of an inclined plane ► IMA = length of ramp / height of ramp  Or IMA = l / h ► So and object raised 2m by pushing it up a ramp 6m long give us and IMA of:  IMA = l / h= 6 / 2= 3

Screw ► A screw is an inclined plane wrapped around a rod. ► The part that wraps is called the thread. ► The thread is much longer than the rod – giving it a mechanical advantage similar to the ramp.

The wedge ► A wedge is an inclined plane that travels through the object or material.  Ie: axe through wood  Needles, knives, front teeth ► The longer and narrower the wedge, the greater the M.A.