Mechanical Advantage

The number of times a machine multiplies your effort force.

Mechanical Advantage

– Example: If you push on the handle of a car jack with a force of 30 lbs and the jack lifts a 3000 lb car, what is the jack’s mechanical advantage?

– The jack multiplies your effort force by 100 times

What type of Simple Machine is a Car Jack?

Lever• A lever is a rigid bar

that rotates around a fixed point called the fulcrum.

• The bar may be either straight or curved.

• In use, a lever has both an effort (or applied) force and a load (resistant force).

Lever

• Mechanical Advantage Formula:• Input Force / Output Force• Output =R Input =E

1st, 2nd and 3rd class levers

Now it’s your turn

• Answer these questions:• What is the name of your lever?• What Class is your lever?• Why is your lever used?• What is the Mechanical Advantage?• Draw your tool and label your measurements

3 Classes of Levers

• The class of a lever is determined by the location of the effort force and the load relative to the fulcrum

Examples:

• 1st class levers: scissors, pliers, seesaw

• 2nd Class Levers: Wheelbarrow, bottle opener

Examples

• 3rd Class Lever: arm, tongs, mouse trap, bb bat

Mechanical Advantage Inclined Plane

Mechanical Advantage FormulaInclined Plane

• Output Force/ Input Force• Slope/ Height

Answer these questions:

• Name of Inclined Plane• Why is it used?• MA• Draw and Label

Mouse Trap

• Lets put together Mouse Trap• On a piece of paper label the Levers and

Wedges.• Figure out the Mechanical Advantage• It this compound saving us any effort?

Wedge

• Mechanical Advantage of Wedge: Divide the Length of the Slope by the thickness of the width.

• Output Force/ Input Force

• Name of Wedge• Why its used• MA• Draw and label

Screw

• Mechanical Advantage: circumference of the top divided by the pitch of the threads.

• Pitch's are the distances between threads.

Screw

• What is the name of your screw• Why is it used?• MA• Draw and label

Wheel and Axle

• The mechanical advantage of a wheel and axle is the ratio of the radius of the wheel to the radius of the axle.

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Wheel and Axle

• In the wheel and axle illustrated in the previous slide, the radius of the wheel is five times larger than the radius of the axle. Therefore, the mechanical advantage is 5:1 or 5.

Answer the Questions:

• Name of Wheel and Axle• Why is it used?• MA• Draw and Label

Gears and Wheel and Axles

• Each gear in a series reverses the direction of rotation of the previous gear. The smaller gear will always turn faster than the larger gear.

Pulleys

Fixed Pulley Movable Pulley

A fixed pulley changes the direction of a force; however, it does not create a mechanical advantage

The mechanical advantage of a moveable pulley is equal to the number of ropes that support the moveable pulley.

When you slip on ice, your foot kicks paddle (A), lowering finger (B), snapping turtle (C) extends neck to bite finger, opening ice tongs (D) and dropping pillow (E), thus allowing you to fall on something soft.