Getting the Wheels Turning

The Perfect Engine

The main purpose of an engine is to get more out of it than you put into it. Otherwise what's the point. Many engines today consume natural resources. The varying cost of a natural resource could make an engine efficient one day and inefficient the next. The ideal engine has an unlimited and free source of energy to run it. Windmills and waterwheels come close, but the flow of water and wind at some point can vary or stop, which affects the reliability of getting power when you need it.

Waterwheels and Windmills

What's great about a water wheel is that you can dip on edge of the wheel into the water and off you go. The wheel rotates on its axis.

With a wind mill typically the spokes are shaped in such a way as to propel the system. A water turbine like those at a dam work the same way. With a windmill the wind direction varies so the position of the blades changes to accommodate for this variation to places the blades at the correct angle to the wind force for highest efficiency.

Gravity and weather are major players with a water wheel. Gravity brings water down a slope and past the water wheel and weather is counted on to return the water back up the slope again.

Talking about Earth's Gravity

Earths gravity varies due to the distance from the center of the earth. Gravity (G) at sea level is 9.8 m/(sec squared). G is an acceleration. The force of gravity on an object though depends on the mass and relative location of all other matter, F=mG.

Interaction of Gravity of Massive Bodies

Earth isn't the only massive body around. We know that the Moon's gravity effects the tides. If you've been to the Bay of Fundy in Nova Scotia, it's pretty cool to see it go from a bay to a mud pit due to the tide going out.

Variation Due to Resistance

Acceleration due to gravity of free falling objects is the same for any object, no matter what its mass is. There can be other forces acting on the objects due to their size, structure, and what they are moving through that will cause a resistance, so the observed acceleration of the falling objects can be different due to other effects besides gravity.

Gravity on the Playground

With gravity we can see on a teeter tauter that if there is more torque on one side than the other there is rotation about the axle. The torque can be from more mass on one side than the other or due to the distance of the mass from the axis of rotation.

Center of Gravity

The mass of an entire structure (any structure) no matter what its shape may be, can be quantified and located at a particular point called the object's center of gravity. When supported at this point the object will not move or fall over. When supported at any other point of the object, the object will rotate and come to rest with the attachment point, the center of gravity, and the source of gravity all being in a line.