Today I ended Grade 8 Science with a review.
Today I learned about materials and structures. The stress of a material is simply the force divided by the cross sectional area over which it is applied. The strain of a material is the ratio of how much the material deforms (deformation) and the original state of the material.
Today I learned about measuring energy usage. I learned what’s inside a wind turbine. Almost all the turbines in use today are horizontal axis machines. Which have a three bladed rotor, spinning at a vertical plane. Attached to the front of a box which is called the nacelle. Inside the nacelle is a generator, often a gearbox and occasionally a high-voltage transformer. And the whole thing sits on top of a tower, which is mainly there to keep the blades from digging a hole. Wind turbines are mostly classed by their power output. While wind farm may use many sub-megawatt turbines each producing 400-600 kilowatts each. Or a few multi-megawatt turbines producing maybe up to three megawatts a unit.
Today I learned about some simple machines. The lever is made out of three basic components. The force arm which refers to the distance between the point at which the force is applied. The fulcrum and the resistance arm or the distance between the points where the resistance is applied and the fulcrum. There are three classes of lever. The first class can be used to amplify speed and strength. The fulcrum is between the point of force and the resistance. A second class lever is characterized by having the fulcrum at one end of the lever and the force at the opposite end with the resistance located between them. A good example of a class two lever is actually a wheelbarrow. The third class lever is characterized by having the fulcrum at one end of the lever and the resistance on the other end with the force between them. Most of the levers in our third class levers. For example our arms, our shoulders are the fulcrum, the forces are our muscles, and the resistance could be water if you’re swimming or a weight.
Today I learned about the engineering concept of energy. What is energy? Energy makes things happen, it’s the ability to do work. energy can be converted into different forms and shapes. There are main two types of energy, kinetic and potential energy. When you think of kinetic energy think of movement. When you think of potential energy think of stored energy. My teacher showed me some examples of kinetic energy and potential energy. However he put explosions on one side representing kinetic energy and a gas station on the other side representing “potential energy”. I know he was trying to say that the gas in a gas station could “potentially” power your car. However what I got from it was that the gas station could potentially explode. There are other types of energy like, thermal energy, chemical energy, nuclear energy, electrical energy and electromagnetic energy.
Today I did a review.
Today I learned about newton’s three laws of motion. Newton’s laws of motion explain the interaction between forces and objects. Newton’s first law states that an object will remain in it’s current state of rest, until acted upon by an unbalanced force. Newton’s second law of motion states that the force equals the mass times the acceleration. Newton’s third law of motion states for every action there is an equal and opposite reaction.