Simple Machines
Simple machines have the ability to ease a load by changing the magnitude or direction of the force applied to it. It does not change the amount of work done or the energy. Energy is always conserved. If the work stays the same, the output force lessens while the direction increases.
There are two categories of simple machines. The first one is the inclined plane family including the ramp, the wedge, and the screw. A ramp is an inclined plane the aids in moving heavy objects more easily. It increases the distance you have to push something, but decreases the amount of input force required to move the object. A wedge holds things together or is able to split things apart. A screw is an inclined plan wrapped around a nail. All of these simple machines increase the distance you have to move an object, but decreases the input force needed to move it.
The second category is the lever family. A lever increases the distance of a force determined by the position of the fulcrum of the lever. A wheel and axle is a level that rotates in a complete circle. A pulley is a rope wrapped around a wheel and changes the direction of the force on an object. The greater number of ropes used, the less force needed to move the object. The less force you use in a simple machine, the greater the distance the force has to travel.
The equations for simple machines are as follows..
Force(input) * Distance(input) = Force(output) * Distance(output)
Efficiency = ( Work(output) / Work(input) ) * 100%
Mechanical Advantage = Force(output) / Force(input)
Ideal Mechanical Advantage = Distance(input) / Distance(output)
Efficiency = Mechanical Advantage / Ideal Mechanical Advantage
To learn more about simple machines and how they work, you can visit http://www.livescience.com/49106-simple-machines.html.
Gears and Gear Ratios
Gears are basically wheels with interlocking teeth on them. These simple machines change the direction of the force and can even increase speed. Gears act like touching wheels, but gears have teeth to keep them from slipping as they turn together. A gear ratio is used to figure out the number of turns each gear in a pair will make based on the number of teeth each gear has. In a gear ratio, the driving gear's amount of teeth/number of turns goes over the driven gear's amount of teeth/number of turns. The following proportion is used to figure out how many turns a gear would make in a pair.
Turns(output) / Turns(input) = Teeth(input) / Teeth(output)
To increase speed on a racer, the force should be applied to a large gear and have that gear connected to a smaller gear. Going from larger to smaller gears increases the amount of turns the smaller gear would make for each turn the large gear makes. This increases speed for the racer.
On our solar car, we went from a smaller gear to a large gear. The smaller gear that was attached to the motor has 10 teeth. The large gear on the axle has 50 teeth. Using the gear ratio formula of driver over driven, the gear ratio ends up as 10/50, or 1/5. The gear ratio for our solar car ended up as 1:5. For every turn the smaller gear makes, the large gears turns 1/5 of a rotation.
Solar Energy and Photo-voltaic Cells
Solar energy is harnessed from sunlight and converted into mechanical energy that we can use for a multitude of things. In order to understand the process of harnessing and using solar energy, you first need to understand how a solar panel works.
Solar panels are made up of an array of modules that contain multiple photo-voltaic cells. Each photo-voltaic cell is made up of an anti-reflective coating or protective glass layer, a neutral dye layer, a positive electrolyte layer, a catalyst, an then another protective glass layer. A photon from the sunlight strikes the dye inside of the n-type layer and it releases an electron into the external load. The electron transfers its energy and then returns to the photo-voltaic cell through the catalyst into the electrolyte. The electron then returns to the dye in the n-type and the process is repeated. Electrons are freed through photon absorption and pushed across the p-n junction by an electric field. The electric field is created through the migration of the electrons. This process occurs millions of times a second and is used to harness energy from the sun. A more detailed description of the layers of a photo-voltaic cell is as follows.
1. Protective Glass Layer
2. SnO2 Conductive Layer
3. Titanium Dioxide and Sensitized Dye (n-type)
4. Electrolyte, Tri-Iodide (p-type)
5. Catalyst Layer
6. Sno2 Conductive Layer
7. Protective Glass Layer
Electricity
Electricity, in the case of our solar car, references more towards the voltage that is produced by the battery pack on the car and the solar panel. Voltage is measured in volts and is the representative of electrical potential. The voltage of something is the capacity of which is can produce electricity. Electricity is produced through the migration of electrons within the cell. Batteries release electrons through their positive side, into the external load, and back in through its negative side. Photo-voltaic cells release electrons into the external load through the excitement through photons and back into the cell through a catalyst layer. The migration creates an electrical field and increases the voltage. The more external loads, or resistors, in a system, the higher the electrical potential. The increase in voltage of a cell increases the power it produces. Electricity is a relative measurement. The equations for electricity are as follows...
Ohm's Law - V = I * R
V is voltage measured in volts, I is current measured in amps, and R is resistance measured in ohms.
P = I * V
P is power measured in watts, I is current measured in amps, and V is voltage measured in volts.