Any ideas on a simple compund machine to make for a 3rd grade class?

Answer 1

Construct a simple lever with a wooden rod pivoted approx. one foot from the end and mark the other end (lever) at 1 foot intervals to three or four feet. It is then easy to demonstrate how it takes the same weight to lift a pound if the distance is the same to lift it - however, if we are willing to move the lever twice the distance (at the two foot mark on the lever) it only takes half the effort (or a 1/2 pound weight) and so on. A small spring scale can also be used instead of weights.
This clearly demonstrates how a man can jack up a 2000 pound car with just a minimal effort - he is simply moving the jack handle over a great distance with several strokes to move the vehicle just a short distance from the ground.

Answer 2

Perhaps you can make a paper (cardboard) "tricycle" where the small wheel has one half the circumference of the large wheel. Using a mark on each wheel, when it is rolled along it should be clear that the small wheel must make two rotations for each rotation of the large wheel (you need only one small wheel in the model). Then remove the wheels and place them together like gears. The small "gear" must make two rotations for each rotation of the large "gear." Have fun.

Answer 3

A winch pulley system, which could be used to hosit heavy objects on to the back of a truck. It would be very practical and in need in today's workplace. It could have a crank gear system or just a direct pulley system. and a "swing over" so it could be attached to the back-side of a stake body truck.

Answer 4

nope

Answer 5

doorknob