If I use an inclined plane does the amount of work change? Work alone to start. We’ll solve it together in a few minutes It takes 100 N of force to lift a book up 3 m onto a shelf. How much work does it require? If I use an inclined plane does the amount of work change? If I use a 5 m inclined plane to help me, how much force is required? What is the Mechanical Advantage of the inclined plane?

Thursday, 23 April 2015 Sit wherever you want (no supergroups) Glue in pages 69R/70L Make a stack of all your phones on your desk (we are making a ramp out of them later)

Work & Simple Machines

What is WORK? Work is done when a force causes an object to move in the same direction that the force is applied. The formula for work is: W = F X D If there is no movement, there is no work being done!

When is WORK being done? A force must applied to an object (called “effort force” or “input”) The object must move in the same direction as the force.

What is purpose of a machine? To make work seem easier!

How do machines make work easier? They can change the amount of force required. They can change the distance the object has to move. They can also change the direction (allowing you to work WITH gravity rather than against it)

How do machines make work “easier”? Force & Distance have an INVERSE relationship. No machine can increase both force and distance!

How Machines Make Work “Easier” If you increase force, you decrease distance. (W = F x D) If you increase distance, you decrease force required. (W = F x D) Leave force and distance alone- but change the direction that the load moves. (Using gravity!)

Units to Know: Work: Joules (J) Force: Newtons (N) Distance: meters (m)

What is Mechanical Advantage? The number of times a machine multiplies your effort force.

Types of Simple Machines the lever the pulley The wheel and axle The inclined plane.

What’s a LEVER? A simple machine made with a rigid bar free to pivot (move) around a fixed point called a fulcrum

Diagrams of Levers Examples: Scissors, see-saw, Crowbar, pliers Door, bottle opener Examples: Hockey stick, tennis racket, baseball bat, shovel

What’s a PULLEY? A simple machine made with a rope, belt or chain wrapped around a grooved wheel. A pulley works two ways: It can change the direction of a force. It can change the amount of force.

Diagrams of Pulleys Fixed pulley: Movable Pulley:

What’s a Wheel & Axle? Large wheel rigidly secured to smaller wheel, called the axle When one part turns, the other part turns too! If one part turns and the other one does not, it is not a true wheel & axle machine!

What is an Inclined Plane? A simple machine with no moving parts. It is simply a straight slanted surface. ( Ex: a ramp.) IT INCREASES THE DISTANCE TRAVELED but REQUIRES LESS FORCE FROM YOU!!!

Other Types of Inclined Planes: Wedge: separating or holding device Screw: circular inclined plane

Types of Inclined Planes

Formula for Mechanical Advantage: MA= slope / height

WORK always stays CONSTANT! FINAL THOUGHT… WORK always stays CONSTANT! Whether you use a machine or not, the TOTAL WORK done stays the same. What would increase/decrease?