Kenneth M. Klemow, Ph.D. Wilkes University Prepared for BIO/EES 105 Energy in our World

 Overview ◦ Energy defined ◦ Forms of energy  The physical nature of energy ◦ Energy and Newtonian Laws of Motion ◦ Units of measure ◦ Conversions  Terminology pertaining to energy  Overview ◦ Energy defined ◦ Forms of energy  The physical nature of energy ◦ Energy and Newtonian Laws of Motion ◦ Units of measure ◦ Conversions  Terminology pertaining to energy

 Ability to do work  Physicists distinguish between kinetic and potential energy  Energy comes in different forms ◦ Radiation ◦ Mechanical energy ◦ Chemical energy ◦ Atomic energy ◦ Electromagnetic energy ◦ Electrical energy ◦ Heat energy  Ability to do work  Physicists distinguish between kinetic and potential energy  Energy comes in different forms ◦ Radiation ◦ Mechanical energy ◦ Chemical energy ◦ Atomic energy ◦ Electromagnetic energy ◦ Electrical energy ◦ Heat energy

Sir Isaac Newton

 Energy = Force x distance  Force = Acceleration x mass  Acceleration = Speed / time  Speed = Distance / time  Energy = Force x distance  Force = Acceleration x mass  Acceleration = Speed / time  Speed = Distance / time

 Speed = distance / time  Ways of expressing ◦ Miles / hour ◦ Km / hour ◦ Feet / second ◦ Meters / second  Other relationships ◦ Distance = Speed x time ◦ Time = Distance / speed  Velocity is a vector: implies speed and direction  Speed = distance / time  Ways of expressing ◦ Miles / hour ◦ Km / hour ◦ Feet / second ◦ Meters / second  Other relationships ◦ Distance = Speed x time ◦ Time = Distance / speed  Velocity is a vector: implies speed and direction

 1 ft/s = m/s  1 mi/h = m/s  1 km/hr = 0.28 m/s  1 ft/s = m/s  1 mi/h = m/s  1 km/hr = 0.28 m/s

 1. A car drives 72 miles in 120 minutes. What is its velocity in miles per hour?  2. A person runs at 6 miles per hour. How far can that person run in 10 minutes? ◦ Expressed in miles: ◦ Expressed in feet:  3. How long does it take for that person to run 528 feet?  1. A car drives 72 miles in 120 minutes. What is its velocity in miles per hour?  2. A person runs at 6 miles per hour. How far can that person run in 10 minutes? ◦ Expressed in miles: ◦ Expressed in feet:  3. How long does it take for that person to run 528 feet?

 A car is traveling 60 miles per hour. How many feet can it travel in one second?

 Acceleration = Change in velocity / time ◦ Expressed as distance / time X time ◦ Or distance / time 2  Occurs when an object is speeding up or slowing down  Units include ◦ Miles / hour 2 ◦ Km / hour 2 ◦ Feet / second 2 ◦ Meters / second 2  Acceleration = Change in velocity / time ◦ Expressed as distance / time X time ◦ Or distance / time 2  Occurs when an object is speeding up or slowing down  Units include ◦ Miles / hour 2 ◦ Km / hour 2 ◦ Feet / second 2 ◦ Meters / second 2

 1 ft/s 2 = m/s 2  1 m/s 2 = 3.28 ft/s 2  1 ft/s 2 = m/s 2  1 m/s 2 = 3.28 ft/s 2

 A Kia Rio can accelerate to 30 km / hour in 6 seconds. What is its acceleration? ◦ Express in terms of m / second 2  (see Example 2.2 on p. 40)  A Kia Rio can accelerate to 30 km / hour in 6 seconds. What is its acceleration? ◦ Express in terms of m / second 2  (see Example 2.2 on p. 40)

 Velocity = Acceleration X Time  Problem: ◦ Return to the Kia  What is velocity after 1 second?  After 3 seconds?  After 6 seconds?  After 9 seconds?  After 12 seconds?  Velocity = Acceleration X Time  Problem: ◦ Return to the Kia  What is velocity after 1 second?  After 3 seconds?  After 6 seconds?  After 9 seconds?  After 12 seconds?

 Gravity has an acceleration (A grav ) ◦ Metric: 9.8 m/s 2 ◦ English: 32 ft/s 2  Gravity has an acceleration (A grav ) ◦ Metric: 9.8 m/s 2 ◦ English: 32 ft/s 2

 X = (1/2) x A x T 2 (see p. 62 of text for derivation) Problem: Imagine you drop a stone from a cliff, and it takes three seconds to hit the water below. How high was the cliff above the water? How fast was the stone moving when it hit the water?  X = (1/2) x A x T 2 (see p. 62 of text for derivation) Problem: Imagine you drop a stone from a cliff, and it takes three seconds to hit the water below. How high was the cliff above the water? How fast was the stone moving when it hit the water?

 Momentum = mass x velocity  Force = mass x acceleration  Common unit of measure for force: ◦ Newton (N = kg x m / s²)  Other relationships ◦ Mass = Force / acceleration (kg=F/a) ◦ Acceleration = Force / mass (A=F/kg)  Momentum = mass x velocity  Force = mass x acceleration  Common unit of measure for force: ◦ Newton (N = kg x m / s²)  Other relationships ◦ Mass = Force / acceleration (kg=F/a) ◦ Acceleration = Force / mass (A=F/kg)

 A rock having a mass of 2 kg falls into the water from a cliff. What is the force that it exerts? ◦ Does that force vary if the cliff is 50’ high, as opposed to being 100’ high?  A rock having a mass of 2 kg falls into the water from a cliff. What is the force that it exerts? ◦ Does that force vary if the cliff is 50’ high, as opposed to being 100’ high?

 Mass is a property of a body (measure of inertia). ◦ Irrespective of its position relative to gravity. ◦ Often expressed as Kg.  Weight depends on gravity. An object will weigh more on earth than on moon because gravitational force greater on earth. ◦ Weight often considered to be unit of force, expressed as Kg x A grav  Where Kg is mass and A grav is acceleration due to gravity.  Mass is a property of a body (measure of inertia). ◦ Irrespective of its position relative to gravity. ◦ Often expressed as Kg.  Weight depends on gravity. An object will weigh more on earth than on moon because gravitational force greater on earth. ◦ Weight often considered to be unit of force, expressed as Kg x A grav  Where Kg is mass and A grav is acceleration due to gravity.

 1. A body will continue to remain at rest or in motion with a constant velocity unless it is acted upon by an outside force.  2. The acceleration of an object is directly proportional to the net force acting on it, and is inversely proportional to its mass (A = F/Kg).  3. For every action force, there is an equal and opposite reaction force.  1. A body will continue to remain at rest or in motion with a constant velocity unless it is acted upon by an outside force.  2. The acceleration of an object is directly proportional to the net force acting on it, and is inversely proportional to its mass (A = F/Kg).  3. For every action force, there is an equal and opposite reaction force.

 Energy = Force x Distance ◦ Joule (J) = Newton x meter  Energy of an apple 1 m from the floor ◦ Some additional measures of energy  Foot pound = 1.4 J  1 calorie = J  1 BTU = 1054 J  Energy = Force x Distance ◦ Joule (J) = Newton x meter  Energy of an apple 1 m from the floor ◦ Some additional measures of energy  Foot pound = 1.4 J  1 calorie = J  1 BTU = 1054 J

 Potential energy ◦ Stored energy, able to do work if released. Examples include:  Objects placed at an elevation  Water behind dam  Release energy if they fall  Objects placed at mechanical tension  Wound up spring  Release energy if tension is relieved  Chemical bond energy  Organic molecules  Energy released if combusted ◦ Potential energy due to elevation  PE G = weight x height = Kg x A grav x h  Potential energy ◦ Stored energy, able to do work if released. Examples include:  Objects placed at an elevation  Water behind dam  Release energy if they fall  Objects placed at mechanical tension  Wound up spring  Release energy if tension is relieved  Chemical bond energy  Organic molecules  Energy released if combusted ◦ Potential energy due to elevation  PE G = weight x height = Kg x A grav x h

 Kinetic energy ◦ Energy of motion Examples include:  Moving water  Moving catapult ◦ Can be expressed mathematically as  1/2 Kg x v 2  Kinetic energy ◦ Energy of motion Examples include:  Moving water  Moving catapult ◦ Can be expressed mathematically as  1/2 Kg x v 2

 Rate at which energy is produced, used, or transferred. ◦ Expressed as energy per time ◦ Common units include  Watt (J / s)  Ft-lb / sec  Horsepower  1 hp = 550 ft-lbs / sec  1 hp = 746 Watts  Rate at which energy is produced, used, or transferred. ◦ Expressed as energy per time ◦ Common units include  Watt (J / s)  Ft-lb / sec  Horsepower  1 hp = 550 ft-lbs / sec  1 hp = 746 Watts

 Question: A kilowatt hour is a measure of: ◦ Power ◦ Energy ◦ Force ◦ Acceleration ◦ None of the above  Question: A kilowatt hour is a measure of: ◦ Power ◦ Energy ◦ Force ◦ Acceleration ◦ None of the above

 Power = energy / time  Energy = power x time  Power = energy / time  Energy = power x time

 W =  (KE + PE)

 Both have two meanings ◦ Conversion  Translating between different units of measure  Joule Calorie BTU  Changing from one form to another  Chemical energy -> Thermal energy ◦ Conservation  First law of thermodynamics  Energy cannot be created or destroyed, only converted  Reduce wasteful energy consumption  Switch from incandescent to light-emitting diode (LED)  Both have two meanings ◦ Conversion  Translating between different units of measure  Joule Calorie BTU  Changing from one form to another  Chemical energy -> Thermal energy ◦ Conservation  First law of thermodynamics  Energy cannot be created or destroyed, only converted  Reduce wasteful energy consumption  Switch from incandescent to light-emitting diode (LED)

 1 kilowatt hour = 3.60 x 10 6 J  1 barrel oil equivalent = x 10 9 J  1 ton wood equivalent = 9.83 x 10 9 J  1 ton coal equivalent = x 10 9 J  1 ton oil equivalent = x 10 9 J  1 quad (PBtu) = x J  1 kilowatt hour = 3.60 x 10 6 J  1 barrel oil equivalent = x 10 9 J  1 ton wood equivalent = 9.83 x 10 9 J  1 ton coal equivalent = x 10 9 J  1 ton oil equivalent = x 10 9 J  1 quad (PBtu) = x J

 First law: Energy cannot be created nor destroyed, can only be converted (conservation of energy) ◦ In an isolated system, total energy will always remain constant  Second law: No energy conversion is perfect; always get some loss as heat. ◦ Gives direction to a reaction ◦ Get increase in disorder (entropy).  First law: Energy cannot be created nor destroyed, can only be converted (conservation of energy) ◦ In an isolated system, total energy will always remain constant  Second law: No energy conversion is perfect; always get some loss as heat. ◦ Gives direction to a reaction ◦ Get increase in disorder (entropy).

 In system involving movement, always get loss as friction  Thus perpetual motion machines are impossible (yet people still try to invent them)  Waste heat given off to environment ◦ Ultimately go off to space  In system involving movement, always get loss as friction  Thus perpetual motion machines are impossible (yet people still try to invent them)  Waste heat given off to environment ◦ Ultimately go off to space

energy (work) output total energy input X 100 Efficiency Efficiencies can vary from 5% - 95% In multistep processes, efficiency is the product of efficiency of each step. Comparative assessments of energy processes / devices typically take great pains to accurately measure efficiency Efficiencies can vary from 5% - 95% In multistep processes, efficiency is the product of efficiency of each step. Comparative assessments of energy processes / devices typically take great pains to accurately measure efficiency =

 Refer to Table 3.1 on p. 78 of text