Sorry for being late on the post. I should have posted this post yesterday. Before I start I am happy to inform you that I will be opening up my new website after I raise enough money to buy a domain name since I am poor :(. School for me just ended so did final exams so I am completely free from any distractions. So here I go:
Today we will learn about Heat. First of all what is heat? Heat is the transfer of energy from a body with a higher temperature to a body with a lower temperature. Heat is considered in this definition to be a verb and is often confused with thermal energy, which is what makes things "hot". Heat is completely outlined in the four laws of thermodynamics which are:
0th law: "If system A and system B are in thermal equilibrium with system C, systems A and B must be in thermal equilibrium with each other." (thermal equilibrium pretty much means that the two systems have equal temperatures)
1st law: The internal energy of a system always stays constant. This is an addition to the law of conservation of energy that states that energy cannot be created nor destroyed in the universe as a whole. In a specific system, there is always energy that is going in and out of the system, thus making the law of conservation of energy very broad accompanying the entire universe.
2nd law: The entropy in an isolated system that is not in thermal equilibrium is constantly increasing. Entropy refers to the disorder of molecules of a system.
3rd law: The temperature absolute zero is not possible anywhere in the universe. This is true because there would constantly be a transfer of heat to objects. Absolute zero was never reached in history but scientists were very close using special refrigerators, reaching a decimal of a kelvin above zero.
In this unit only two formulas are needed:
Quantity of heat = mass * specific heat capacity * change in temperature
Using the bolded letters into units the heat formula is created: Q = mcΔT
The second formula is much more simple:
Q(in)=Q(out)
This formula says that in a system that is in thermal equilibrium, the amount of heat that left the system is equivalent to the amount of heat that entered the system reconnecting the thermal equilibrium.
The post tomorrow will have an example question that might appear on an AP Physics test.
Sunday, June 10, 2012
Tuesday, June 5, 2012
Next Saturday's Post
Hello everyone of the world. I am just here to congratulate you for earning one more tutorial from me. I am getting help from a friend to do this website so it would be spectacular. Surprisingly this is the shortest post in this brand new blog. Oh you don't know how far boredom can take you, and for me it made me make a blog. I am planning to do a segment on waves and wave physics so STAY TUNED!!
Mechanical Energy Tutorial & Question
Lets start talking about energy. First of all what is energy? Energy is simply a quantity. Energy can be found in many forms for example, sound energy, kinetic energy, chemical energy, and potential energy. In this post I will be going to set ground rules for energy in general and will go into the specifics of mechanical energy, or the sum of the kinetic and potential energy.
You all probably know what kinetic energy (KE) is already. If you don't know kinetic energy is the energy of motion. All objects that are moving have kinetic energy. Potential energy (PE) comes in two forms. One is gravitational potential energy and one is elastic potential energy. Gravitational potential energy is found only when objects are above ground. The energy comes from the constant pull of gravity on an object, and the objects resistance to fall with it. Examples of gravitational potential energy (GPE) are when a roller coaster goes up a hill and when someone climbs a mountain. Gravitation potential energy often has to do with climbing up structures (this is important to remember during tests). Elastic potential energy (EPE) often correlates with things that are stretched out like springs and rubber bands.
In order to understand mechanical energy (ME), one must know the law of conservation of energy, which states in this situation, the sum of the total potential energy and the total kinetic energy of a system is always going to be constant.
Formulas to memorize
ME (always constant in a system)= KE + PE
GPE = mass * height * acceleration due to gravity (on Earth is equal to 9.81 m/s/s)
EPE = (1/2) * k(spring constant) * distance (the spring stretched)
KE = (1/2) * (mass) * (velocity of the object)^2
((1/2)(mass)(velocity1)^2) + (mass*height1*acceleration due to gravity)=((1/2)(mass)(velocity2)^2) + (mass*height2*acceleration due to gravity)
Study these equations very closely before continuing especially the last one, which is the hardest to remember. To familiarize with the technique I will be using go down to the first post.
Sample Cutnell and Johnson 1-Star(aka the second hardest questions in the book) question on Energy
The only reason I am doing a 1 Star question was because the 2 Star questions needed a diagram. However this 1 Star question is fantastic in teaching this concept.
1) Two pole-vaulters just clear the bar at the same height. The first lands at a speed of 8.90 m/s, while the second lands at a speed of 9 m/s. The first vaulter clears the bar at a speed of 1 m/s. Ignore air resistance and friction and determine the speed at which the second vaulter clears the bar.
What we Know
Velocity1=8.90 m/s
Velocity2=9m/s
Top of the Jump Velocity1 = 1m/s
What we Need to Know
Top of the Jump Velocity2?
Formulas Needed to Solve
All of the Formulas needed to solve the problem can be found under "Formulas to memorize" above.
Steps to Solve this 1-Star Cutnell and Johnson Question
First you need to find the height of the bar in order to find the velocity of the second jumper.
The formula can be created from rearranging the final equation in the list.
((8.9 m/s/s)-(1 m/s/s))/(2*9.8 m/s/s) = 3.99 meters high
Knowing the height of the bar, the velocity of the person at the top can be solved.
sqrt (9 m/s/s - (2*9.8 m/s/s)*3.99m) = 1.7 m/s
Wow that was quite a difficult question. Please take sometime to rearrange the formulas and try to solve the question yourself. Be simply doing this question again, it would be much easier on a test to solve the same kind of question. Get ready to learn about something new next week! Good luck and subscribe for more posts! Get ready for a tutorial on heat by Saturday.
You all probably know what kinetic energy (KE) is already. If you don't know kinetic energy is the energy of motion. All objects that are moving have kinetic energy. Potential energy (PE) comes in two forms. One is gravitational potential energy and one is elastic potential energy. Gravitational potential energy is found only when objects are above ground. The energy comes from the constant pull of gravity on an object, and the objects resistance to fall with it. Examples of gravitational potential energy (GPE) are when a roller coaster goes up a hill and when someone climbs a mountain. Gravitation potential energy often has to do with climbing up structures (this is important to remember during tests). Elastic potential energy (EPE) often correlates with things that are stretched out like springs and rubber bands.
In order to understand mechanical energy (ME), one must know the law of conservation of energy, which states in this situation, the sum of the total potential energy and the total kinetic energy of a system is always going to be constant.
Formulas to memorize
ME (always constant in a system)= KE + PE
GPE = mass * height * acceleration due to gravity (on Earth is equal to 9.81 m/s/s)
EPE = (1/2) * k(spring constant) * distance (the spring stretched)
KE = (1/2) * (mass) * (velocity of the object)^2
((1/2)(mass)(velocity1)^2) + (mass*height1*acceleration due to gravity)=((1/2)(mass)(velocity2)^2) + (mass*height2*acceleration due to gravity)
Study these equations very closely before continuing especially the last one, which is the hardest to remember. To familiarize with the technique I will be using go down to the first post.
Sample Cutnell and Johnson 1-Star(aka the second hardest questions in the book) question on Energy
The only reason I am doing a 1 Star question was because the 2 Star questions needed a diagram. However this 1 Star question is fantastic in teaching this concept.
1) Two pole-vaulters just clear the bar at the same height. The first lands at a speed of 8.90 m/s, while the second lands at a speed of 9 m/s. The first vaulter clears the bar at a speed of 1 m/s. Ignore air resistance and friction and determine the speed at which the second vaulter clears the bar.
What we Know
Velocity1=8.90 m/s
Velocity2=9m/s
Top of the Jump Velocity1 = 1m/s
What we Need to Know
Top of the Jump Velocity2?
Formulas Needed to Solve
All of the Formulas needed to solve the problem can be found under "Formulas to memorize" above.
Steps to Solve this 1-Star Cutnell and Johnson Question
First you need to find the height of the bar in order to find the velocity of the second jumper.
The formula can be created from rearranging the final equation in the list.
((8.9 m/s/s)-(1 m/s/s))/(2*9.8 m/s/s) = 3.99 meters high
Knowing the height of the bar, the velocity of the person at the top can be solved.
sqrt (9 m/s/s - (2*9.8 m/s/s)*3.99m) = 1.7 m/s
Wow that was quite a difficult question. Please take sometime to rearrange the formulas and try to solve the question yourself. Be simply doing this question again, it would be much easier on a test to solve the same kind of question. Get ready to learn about something new next week! Good luck and subscribe for more posts! Get ready for a tutorial on heat by Saturday.
Saturday, June 2, 2012
Work and Power Questions
This textbook makes everyone in the high school world struggle. However, I can help with the dreadful 2 star Cutnell and Johnson Questions. People think these Cutnell and Johnson 2 star questions are literally impossible to solve, but with simple critical thinking it is a peace of cake. Every single student who has ever taken physics has dreaded these questions assigned for homework, but if you try you can solve anything.
Before each question, a tutorial will be given that would help the student solve the problem. Explanations and formulas would be given prior to each example question. However for this question a tutorial should not be needed since it is a very basic topic. Once we get deeper into physics, even parts after AP Physics, we should make sure we pay attention to the tutorials, as they are essential for the completion of the question successfully.
1) For example: The motor of a ski boat generates an average power of 7.5 * 10^4 W when the boat is moving at a constant speed of 12 m/s. When the boat is pulling a skier at the same speed the engine must generate an average power of 8.30 * 10^4 W. What is the tension in the tow rope that is pulling the skier?
What my teacher always told us was to write down everything that you know and all of the stuff you want to know. Also she told us to write down what the formula needed in order to solve the question.
What we know
Power = 8.30 * 10^4 W (with the skier)
Power = 7.5 * 10^4 W (without the skier)
Velocity = 12 m/s (constant)
What we want to know
The tension of the rope pulling the skier.
What formula is needed to solve this equation
Power = Work / Time = Force * Velocity
Work = Force * Distance
Steps to Solve the 2-Star Cutnell and Johnson Question
The amount of power needed to pull the skier can be found by subtracting the powers with the skier and without the skier.
8.30 * 10^4 W (with the skier) - 7.5 * 10^4 W (without the skier) =8 * 10^3
Since the Power = Force * Velocity, the tension (force) can be found by plugging in the units and solving this equation.
Tension = (8 * 10^3 W)/(12 m/s)
Tension = 666.6 Newtons
BOOM! You solved one of the hardest physics problems that you will ever attempt in high school.
Now that I introduced the Cutnell and Johnson 2-Star question (aka the hardest questions in the book), from now on I recommend you, the students, to actually attempt to solve the question before looking at the summary. So this means you should cover up the answer and solve the question before looking onwards. This is VERY important for your success in physics. Please subscribe and you will be given tutorials and practice problems every week.
Open up this picture and study it since it gives valuable information on Work, Energy, and Power.
Before each question, a tutorial will be given that would help the student solve the problem. Explanations and formulas would be given prior to each example question. However for this question a tutorial should not be needed since it is a very basic topic. Once we get deeper into physics, even parts after AP Physics, we should make sure we pay attention to the tutorials, as they are essential for the completion of the question successfully.
1) For example: The motor of a ski boat generates an average power of 7.5 * 10^4 W when the boat is moving at a constant speed of 12 m/s. When the boat is pulling a skier at the same speed the engine must generate an average power of 8.30 * 10^4 W. What is the tension in the tow rope that is pulling the skier?
What my teacher always told us was to write down everything that you know and all of the stuff you want to know. Also she told us to write down what the formula needed in order to solve the question.
What we know
Power = 8.30 * 10^4 W (with the skier)
Power = 7.5 * 10^4 W (without the skier)
Velocity = 12 m/s (constant)
What we want to know
The tension of the rope pulling the skier.
What formula is needed to solve this equation
Power = Work / Time = Force * Velocity
Work = Force * Distance
Steps to Solve the 2-Star Cutnell and Johnson Question
The amount of power needed to pull the skier can be found by subtracting the powers with the skier and without the skier.
8.30 * 10^4 W (with the skier) - 7.5 * 10^4 W (without the skier) =8 * 10^3
Since the Power = Force * Velocity, the tension (force) can be found by plugging in the units and solving this equation.
Tension = (8 * 10^3 W)/(12 m/s)
Tension = 666.6 Newtons
BOOM! You solved one of the hardest physics problems that you will ever attempt in high school.
Now that I introduced the Cutnell and Johnson 2-Star question (aka the hardest questions in the book), from now on I recommend you, the students, to actually attempt to solve the question before looking at the summary. So this means you should cover up the answer and solve the question before looking onwards. This is VERY important for your success in physics. Please subscribe and you will be given tutorials and practice problems every week.
Open up this picture and study it since it gives valuable information on Work, Energy, and Power.
Physics Questions...
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