Force is a push or pull that gives energy to an object. Gravity is a force pulling us down toward the ground that gives us our weight. The amount of weight or force is put upon one single point makes a big difference in different situations. For instance, imagine lying on a bed of nails! Nails have been created with a large head to hit with the hammer and a small point that concentrated the force or energy of the hammer into one tiny spot so that the nail will push through really hard materials like wood. So, naturally, one would presume lying on a bed of nails will be not very good for his/her long term health! However if we understand concentration vs. distribution of force we see that the important part of a nail is that it pushes all the weight on a SMALL area. If we instead spread the force of our entire weight onto MANY nails at once, the force would be distributed over a LARGE area - evenly spreading the weight between all the nails at once!

The pressure that is applied is equal to the amount of force divided by the area (P=F/A). So, if the area is increased, and you use the same amount of force (your body laying on the nails), less pressure is created on each individual point.

On the other side of the coin is concentration of force. We already looked at nails, but this is also how axes work - by concentrating all the force into a small sharp area, you can chop down a tree. Could you chop down a tree with the same amount of muscles and just a baseball bat? No way!

Friction is resistance between moving objects. When a leaning pile of papers begins to fall off a desk, each paper slides easily and glides to the floor. That’s because there’s very little friction. Friction can mean its easier or harder for two objects to move when their touching. What makes a car move? Tires. Tires reduce the amount of friction between the weight of a car and the surface of a road. If your car has no tires, how easy is it to push it down the road? What if the car has no tires but the road is covered with ice? What if your car does have tires AND the road is covered with ice?

The Center of Gravity or Center of Mass is an imaginary point where an object’s weight is concentrated. For humans it’s right around your bellybutton. If your center of mass is supported by a base of support (like your feet) you can stand perfectly balanced with no problem. However, if your center of mass is not over your base of support (like if you stand on one foot or someone take a chair out from under you!) you will loose your balance.

An architectural dome is able to support weight from the top by spreading the weight out along the entire dome, which lessens impact of the full weight. Domes have been used for centuries in large buildings. The idea for domes comes from the natural strength of the shape of an egg. The egg’s amazing structure is what makes it so strong. The shape explains why an egg can withstand compression (like squeezing it in your hand) without breaking. Especially force from top & bottom; which happens when an egg falls from the hen to the nest. But when you put pressure across just eh middle or on a one specific point, the egg will easily break! That’s why most folks crack an egg from the center across a hard surface to open it!

The lever is a simple machine made with a bar free to move about a fixed point called a fulcrum. Levers help make work easier. The lever makes it easier to move objects because it take less force to move it. The closer the fulcrum is to the load the less force you have to use. The lever consists of three parts: the fulcrum, load, and a rod.