LESSON 4 Describing Basic Physical Science Laws Applied in Agricultural Mechanics

Next Generation Science/Common Cores Standards Addressd! zCCSS.EL A Literacy. RST.9 ‐ n Translate quantitative or technical information expressed in words in a text into visual form (e.g., a table or chart) and translate information expressed visually or mathematically (e.g., in an equation) into words. zCCSS.EL A Literacy. RST.11 ‐ 12.3 Follow precisely a complex multistep procedure when carrying out experiments, taking measurements, or performing technical tasks; analyze the specific results based on explanations in the text zHSNQ.A.1 Use units as a way to understand problems and to guide the solution of multi ‐ step problems; choose and interpret units consistently in formulas; choose and interpret the scale and the origin in graphs and data displays. (HS ‐ PS1 ‐ 2),(HS ‐ PS1 ‐ 4),(HS ‐ PS1 ‐ 5),(HS ‐ PS1 ‐ 7)

Bell Work - STUDENT LEARNING OBJECTIVES: o1. Explain how Boyle’s Law relates to agricultural mechanics. o2. Explain how the Law of Conservation of Energy relates to agricultural mechanics. o3. Explain how Ohm’s Law relates to agricultural mechanics. o4. Explain how Pascal’s Law relates to agricultural mechanics.

TERMS zAmperes zRobert Boyle zBoyle’s Law zCompression ratio zElectrons zHorsepower zLaw of Conservation of Energy

TERMS zMolecules zOhm’s Law zBlaise Pascal zPascal’s Law zResistance zTorque zVoltage

Interest Approach zWhat are some laws of science that you are familiar with? (law of gravity) zDiscuss how an idea or theory becomes a law.

Objective #1: zWhat is Boyle’s Law and how does it relate to agricultural mechanics?

Robert Boyle zRobert Boyle, an English scientist, discovered in 1662 that the pressure a gas exerts can be increased by reducing its volume while holding temperature constant.

Robert Boyle zThis is possible because all matter, including gases, is made up of tiny particles called molecules. zBoyle was able to develop a theory, which was later proven to be a law. zThat law is called Boyle’s Law

Boyle’s Law zStates that the product of pressure times volume in a gas at constant temperature is a constant.

Boyle’s Law zThis means that when the volume of gas is decreased, the gas molecules bombard the container walls more frequently. zThe result is an increase in pressure against the walls of the container.

Boyle’s Law zThe volume of a gas is inversely proportional to the pressure applied to the gas. zThat means that pressure increases at the same rate that volume decreases.

Boyle’s Law zBoyle’s Law is expressed in the formula P1 x V1 = P2 x V2 where P1 = original pressure of a gas; V1 = original volume of a gas; P2 = pressure of a gas under new conditions; V2 = volume of a gas under new conditions.

Boyle’s Law zBoyle’s Law explains pressure- volume relationships for both decreasing and increasing volumes.

Boyle’s Law zOne way this law is related to agriculture mechanics is in internal combustion engines.

Boyle’s Law zIn internal combustion engines, the compression ratio is the volume of air in a cylinder before compression compared to the volume of air in the cylinder after compression.

Boyle’s Law zThis law provides an explanation on why diesel engines are more powerful than gasoline engines.

Boyle’s Law zDiesel engines normally have a compression ratio of 16 to 1 or higher, while a gasoline engine’s ratio is normally 8 to 1. zThe higher ratio equates to more power.

Objective #2: zWhat is the Law of Conservation of Energy and how does it relate to agricultural mechanics?

Law of Conservation of Energy zPhysical science laws govern much of what agricultural mechanics is able to do with machines. zOne such law is the Law of Conservation of Energy.

Law of Conservation of Energy zThe Law of Conservation of Energy states the energy cannot be created nor destroyed. zThis tells us that energy output of a system cannot exceed the energy input to the system.

Law of Conservation of Energy zThis law of science is most evident in dealing with power transmission systems.

Law of Conservation of Energy zMost applications of power begin with the rotating of shafts. zThe amount of work being done by rotating shaft can be measured. zThe unit used to do such measurement is called horsepower.

Law of Conservation of Energy zHorsepower is defined as the force needed to lift 550 pounds, one foot high, in one second. zThe horsepower of most applications is finite.

Law of Conservation of Energy zTherefore, tradeoffs must be made between torque (a turning or twisting force) and speed. zThe Law of Conservation of Energy governs these tradeoffs.

Objective #3: zWhat is Ohm’s Law and how does it relate to agricultural mechanics?

Ohm’s Law zThe flow of electrons (charged particles) through a conductor, provides the energy needed to power many machines in agriculture and elsewhere.

Ohm’s Law zAn energy source provides the push needed to move these electrons through the conductor. zThis movement of electrons is called voltage.

Ohm’s Law zVoltage may be compared to the available water that can flow through a garden hose

Ohm’s Law zAmperes is a measure of the rate at which electrons move through the conductor. zIn the garden hose examples, amperage may be compared to the rate at which water actually flows through the hose.

Ohm’s Law zThe amount of energy needed to push the electrons through the conductor is dependent on the conductor’s resistance or opposition to flow. zThis resistance is measured in ohms.

Ohm’s Law zOhm’s Law, first proposed by G.S. Ohm, a German scientist, states that the amount of current in an electrical circuit is directly proportional to the voltage applied across the circuit and inversely proportional to the resistance of the circuit.

Ohm’s Law zThis means that as voltage increases, the flow of current (amps) increases. zBut, as resistance (ohms) increases, the current flow (amps) decreases.

Ohm’s Law zOhm’s Law is expressed in the following formula: E = I x R where E = Voltage; I = Current (measured in amperes) ; R = Resistance (measured in ohms).

Objective #4: zWhat is Pascal’s Law and how does it relate to agricultural mechanics?

Pascal’s Law zIn 1653, Blaise Pascal, a French scientist formulated the fundamental law that explains the operation of hydraulic equipment.

Pascal’s Law zPascal’s Law states that pressure applied to a confined fluid is transmitted undiminished in all directions, acts with equal force on equal areas, and acts at right angles to the walls of the container.

Pascal’s Law z An example of this law can be seen by using a container of liquid. zA 10-lb force applied to the stopper (having an area of 1 in 2 ) will result in a pressure of 10 lbs per in 2 being exerted by the fluid.

Review z1. Explain how Boyle’s Law relates to agricultural mechanics. z2. Explain how the Law of Conservation of Energy relates to agricultural mechanics.

Review z3. Explain how Ohm’s Law relates to agricultural mechanics. z4. Explain how Pascal’s Law relates to agricultural mechanics.

The End!