S P H 4 C – U N I T # 2 M E C H A N I C A L S Y S T E M S

THE INCLINED PLANE FAMILY OF MACHINES

LEARNING GOALS AND SUCCESS CRITERIA

Today I will…

• Define an inclined plane

• Identify which member of the inclined plane family a simple machine belongs to

THE INCLINED PLANE FAMILY OF MACHINES

An inclined plane is a ramp that increases the load that can be moved by an effort force. The force required to move an object up a ramp is less than the force needed to lift it vertically upward. For example, think of how much easier it is to walk up a stairway than to climb a ladder.

Inclined Plane•A ramp•Increases the load that can be moved by an effort force

THE INCLINED PLANE FAMILY OF MACHINES

A wedge is a double inclined plane that increases the applied force, for example, in an axe blow.

Wedge•A double inclined plane

THE INCLINED PLANE FAMILY OF MACHINES – DYK?

In recent years, large chunks of Antarctica’s ice shelves have broken off. Scientists have discovered that a wedge effect causes the ice to break. Because of global warming, higher summer temperatures cause surface ice to melt. Some of the resulting water seeps into cracks in the ice. This water, acting as a “liquid wedge,” puts extra pressure on the ice. The water cracks the ice further and pushes the chunks of ice apart.

THE INCLINED PLANE FAMILY OF MACHINES – DYK?

Some of the chunks pushed away are huge; one from the Larsen Ice Shelf was 200 m thick and covered a surface area half the size of Prince Edward Island.

THE INCLINED PLANE FAMILY OF MACHINES

A screw is an inclined plane wrapped around a central shaft. It too, increases the applied force.

Screw•An inclined plane wrapped around a central shaft.

THE INCLINED PLANE FAMILY OF MACHINES

The screw is one of the two simple machines of the car jack. The handle and central shaft act as a wheel and axle. Thus, the car jack is an example of a compound machine. A compound machine is a machine made of two or more simple machines.

Compound Machine•A machine made of two or more simple machines.

THE INCLINED PLANE FAMILY OF MACHINES

Practice1. State which simple machine forms the basis of each of the

following:a) A doorstopb) An escalatorc) A mountain highwayd) A hand-held pencil sharpener

a) wedgeb) Inclined planec) Screwd) Screw or wedge

HOMEWORK

Read: Pg. 75-76Practice Problems: Pg. 77 #6, 8