Revision of magnets and machines

Which machine can push things apart?

• screw

• wheel and axle

• wedge

• inclined plane

What's the name of this magnet?_____

Which machine can make it easy to move things by rolling them and reducing friction(阻力)？

• wedge

• screw

• wheel and axle

• pulley

Earth's magnetic field has_____poles.

Structure of the electromagnet includes________.

• coil,core and switch(开关)

• current(电流)+paperclips

• core,bar magnet

• current+core+coils

Identify the simple machine in the picture.

• screw

• wedge

• pulley

• lever

A wheelchair ramp would be an example of which type of simple machine?

• wheel and axle

• inclined plane

• pulley

• wedge

Compound machines(组合机械) consist of（由......组成） two or more simple machines combined together to make work easier and increase the mechanical advantage（力学上的优势）. What two simple machines are used in a wheelbarrow(独轮手推车)?

• Inclined plane and a lever

• a pulley and wheel/axle

• a lever and a pulley

• a lever and wheel/axle

How is magnet used in the picture?

• show direction

• lift magnetic things

• find plastic rubbish

• store information

Bar magnets have two poles. What are they?

• red and blue

• east and west

• red and green

• north and south