Machines and Mechanics
Machines like diggers, concrete mixers, cranes and excavators help to create buildings by shifting large heavy objects and materials around. Early prehistoric machines were ramps, and axes, later came the wheel, pulleys and levers. The Industrial Revolution brought more complex machines such as steam engines. Steam has made so many things possible that we now take for granted.
Movers and Shakers, in See Inside How Things Work written by Conrad Mason and illustrated by Colin King, published by Usborne Books
Activity: Constructing with Spaghetti and Marshmallow
With thanks to The Marshmallow Challenge, invented by Peter Skillman and popularized by Tom Wujec.
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Here’s the science
Spaghetti is not very strong and can quickly snap. If lots spaghetti is used then each piece takes a little of the weight of the construction. This means that force needs to be distributed carefully to avoid collapse. Triangular shapes work best because the force of the load is equally distributed along all three sides. Marshmallows introduce mass to the construction, but too many marshmallows to one side and the construction will collapse.
Forces and Motion
Machines are physical systems that use power to perform actions by applying forces and controlling movement, often using power from sources like engines or motors. Gears, levers, cams, and screws are all examples of mechanisms. Screws are used to hold things together and keep them strong. Cams and cranks are simple mechanisms that set objects like wheels into motion.
Cams and Cranks in The Way Things Work by David Macaulay, published by DK
Activity: Rice in a Bottle, Friction Demo
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Here’s the Science
By compressing the rice grains, air pockets are removed leaving less space for the rice grains to move. When the pencil is inserted the rice grains press against each other causing friction. Friction is the force that appears when one surface is rubbed against another. This static friction resists motion and holds the pencil firmly in place. The frictional force of the rice is greater than the downward pull of gravity on the bottle, allowing you to lift it.