Here is a hyperlink where you can do a webquest to learn more about Kinematics (terminal velocity). It is in relation to the force of gravity and other forces it goes through.
Terminal Velocity webquest.
Kudos to clement, eugene, latha & ying xian for the webquest
Tuesday, April 6, 2010
Saturday, April 3, 2010
Experiment using a smart pulley in determining the gravitational constant-g
Background information
An object moving through a fluid experiences a resistive force, or drag, that is proportional to the viscosity of the fluid. If the object is moving slowly enough, the drag force is proportional to the speed v. if the object is a sphere of radius r, the force is
F = 6πnrv
An object moving through a fluid experiences a resistive force, or drag, that is proportional to the viscosity of the fluid. If the object is moving slowly enough, the drag force is proportional to the speed v. if the object is a sphere of radius r, the force is
F = 6πnrv
Where n is the coefficient of viscosity. This equation is known as Stoke’s law.
By relating Newton’s second law and Stoke’s law, determine the value of g (gravitational constant) in ms-2.
By relating Newton’s second law and Stoke’s law, determine the value of g (gravitational constant) in ms-2.
*Hint* When the object reaches terminal velocity, the sum of forces will result in no net force, thus producing a terminal velocity.
Fgrav = Fbuoyant + Fdrag
Where Fbuoyant = Weight of fluid displaced (Archimedes’ principle)
Where Fbuoyant = Weight of fluid displaced (Archimedes’ principle)
Apparatus
· Smart pulley system (connected to the computer with science workshop)
· Data logging interface (with attached cables)
· 1 m long with a 7 cm diameter hollow cylindrical tube (rubber stopper at bottom)
· Retort stand (with two clamps)
· Pendulum (tied to string)
· Fluid medium (Air, water or glycerol)
· Dead weight
Experimental Procedure
1. Set up the apparatus as shown in the diagram
2. Open the science workshop program and drag the motion sensor interface icon to “input 1”
3. Select the graphing option on the interface and check the options for “Distance-time, velocity-time and acceleration-time”.
4. Before releasing the pendulum from dropping, get your lab partner to hold the ball at start point close to sensor.
5. Press the record button on the computer.
6. Release the pendulum and press the stop button as soon as the pendulum hits the bottom stopper.
7. The results would be available for analysis on the graph obtained.
Results and questions
1. Print out the various graphs obtained from the experimental proceedings.
2. Explain the trend of the values obtained on the acceleration time graph.
3. Calculate the value of g from the velocity-time graph obtained. What conclusions can you draw from the 2 graphs (Do you see any similarity/anomaly?)
4. Calculate the force due to gravity by relating Stoke’s law and Newton’s law.
5. Using Newton’s second law, find g.
Experiment using a motion sensor in determining the gravitational constant- g
Background information
All objects undergoing freefall would experience acceleration-downwards (toward the axis of the earth) due to gravity. The coined term, “gravitational acceleration” has conventionally been taught at your level to assume a value of 10ms-2. In this experiment, you would find out the value of “g”. You will be required to use your prior knowledge of kinematics in determining the value of acceleration by using an appropriately plotted distance-time graph. After doing so, you will be required to critique on the velocity in which the object is free falling, and explain why the majority of the scientific community classifies the quantity “g”-gravitational acceleration- as a constant.
Standard gravity, usually denoted by g0 or gn, is the nominal acceleration due to gravity at the Earth's surface at sea level, defined to be precisely 9.80665 m/s2 (~32.174 ft/s2). This value was established by the 3rd CGPM (1901, CR 70).
The symbol g is sometimes also used for standard gravity, but g strictly means the local acceleration due to gravity, which varies depending on one's position on Earth (see Earth's gravity). The symbol g should not be confused with G, the gravitational constant, or g, the abbreviation for gram. The g (sometimes written "gee") is also used as a unit of acceleration, with the value defined as above; see g-force.
The value of g0 defined above is a nominal midrange value on Earth, representing the acceleration of a body in free fall at sea level at a geodetic latitude of about 45.5°. It is larger in magnitude than the average sea level acceleration on Earth, which is about 9.797645 m/s2. Although the actual strength of gravity on Earth varies according to location, for weights and measures and many calculation purposes the standard gravity figure is used.
The SI unit of acceleration due to gravity (or, indeed, any acceleration), namely meters per square second, can also be written as newton per kilogram. The numeric value stays the same: gn = 9.80665 N/kg. This alternative representation can be understood by noting that the gravitational force acting on an object at the Earth's surface is proportional to the mass of the object: for each kilogram of mass, the Earth exerts a nominal force of 9.80665 newtons (though, as stated, the precise value varies depending on location).
Because the acceleration due to gravity is the force acting on unit mass (in SI units, 1 kg) it is often referred to as the gravitational field in analogy with the electric field which is the electrostatic force on a unit charge.
In physics, gravitational acceleration is the specific force or acceleration on an object caused by gravity. In a vacuum, all small bodies accelerate in a gravitational field at the same rate relative to the center of mass. This is true regardless of the mass or composition of the body. On the surface of the Earth, all objects fall with an acceleration between 9.78 and 9.82 m/s2 depending on latitude, with a conventional standard value of exactly 9.80665 m/s2 (approx. 32.174 ft/s2). Objects with low densities do not accelerate as rapidly due to buoyancy and air resistance. In a vacuum all small objects have same acceleration regardless of density
Apparatus
· Retort stand
· Clamps for the retort stand
· Computer equipped with the science workshop software
· Data logging interface
· Motion sensor
· Connecting cables for the data logging interface and motion sensor
· Ball/object to be dropped (Free fall)
Experimental proceedings
1. Set up the apparatus as shown in the diagram
All objects undergoing freefall would experience acceleration-downwards (toward the axis of the earth) due to gravity. The coined term, “gravitational acceleration” has conventionally been taught at your level to assume a value of 10ms-2. In this experiment, you would find out the value of “g”. You will be required to use your prior knowledge of kinematics in determining the value of acceleration by using an appropriately plotted distance-time graph. After doing so, you will be required to critique on the velocity in which the object is free falling, and explain why the majority of the scientific community classifies the quantity “g”-gravitational acceleration- as a constant.
Standard gravity, usually denoted by g0 or gn, is the nominal acceleration due to gravity at the Earth's surface at sea level, defined to be precisely 9.80665 m/s2 (~32.174 ft/s2). This value was established by the 3rd CGPM (1901, CR 70).
The symbol g is sometimes also used for standard gravity, but g strictly means the local acceleration due to gravity, which varies depending on one's position on Earth (see Earth's gravity). The symbol g should not be confused with G, the gravitational constant, or g, the abbreviation for gram. The g (sometimes written "gee") is also used as a unit of acceleration, with the value defined as above; see g-force.
The value of g0 defined above is a nominal midrange value on Earth, representing the acceleration of a body in free fall at sea level at a geodetic latitude of about 45.5°. It is larger in magnitude than the average sea level acceleration on Earth, which is about 9.797645 m/s2. Although the actual strength of gravity on Earth varies according to location, for weights and measures and many calculation purposes the standard gravity figure is used.
The SI unit of acceleration due to gravity (or, indeed, any acceleration), namely meters per square second, can also be written as newton per kilogram. The numeric value stays the same: gn = 9.80665 N/kg. This alternative representation can be understood by noting that the gravitational force acting on an object at the Earth's surface is proportional to the mass of the object: for each kilogram of mass, the Earth exerts a nominal force of 9.80665 newtons (though, as stated, the precise value varies depending on location).
Because the acceleration due to gravity is the force acting on unit mass (in SI units, 1 kg) it is often referred to as the gravitational field in analogy with the electric field which is the electrostatic force on a unit charge.
In physics, gravitational acceleration is the specific force or acceleration on an object caused by gravity. In a vacuum, all small bodies accelerate in a gravitational field at the same rate relative to the center of mass. This is true regardless of the mass or composition of the body. On the surface of the Earth, all objects fall with an acceleration between 9.78 and 9.82 m/s2 depending on latitude, with a conventional standard value of exactly 9.80665 m/s2 (approx. 32.174 ft/s2). Objects with low densities do not accelerate as rapidly due to buoyancy and air resistance. In a vacuum all small objects have same acceleration regardless of density
Apparatus
· Retort stand
· Clamps for the retort stand
· Computer equipped with the science workshop software
· Data logging interface
· Motion sensor
· Connecting cables for the data logging interface and motion sensor
· Ball/object to be dropped (Free fall)
Experimental proceedings
1. Set up the apparatus as shown in the diagram
2. Open up the science workshop program and drag the motion sensor interface icon to “input 1”
3. Select the graphing option on the interface and check the options for “Distance-time, velocity-time, and acceleration-time”
4. Before releasing the ball from free fall, get your lab partner to hold the ball at start point close to the sensor.
5. Press the record button on the computer.
6. Release the ball, and press the stop button as soon as the ball hits the floor and rebounds for a 2nd trip downwards.
7. The results would be available for analysis on the graphs obtained.
Results and questions
1. Print out the various graphs obtained from the experimental proceedings
2. Explain the trend of the values obtained on the acceleration time graph.
3. Calculate the value of g from the velocity time graph obtained. What conclusions can you draw from the 2 graphs (Do you see any similarity/anomaly?)
4. Calculate the force the ground experiences when the ball hits the ground for a rebound, explaining your answer with reference to Newton’s second law.
5. What can you say about Newton’s third law with respect to how the ball rebounds for a slight return.
Brief summary on the Science workshop software
Dear students.
Before proceeding with your experiments, have a look at this video so that you have a better understanding of what you're supposed to do in the following session.
Before proceeding with your experiments, have a look at this video so that you have a better understanding of what you're supposed to do in the following session.
Wednesday, March 31, 2010
Useful youtube videos!
Dear students!
To fully comprehend the wonders of Physics, you'd first have to understand that there are no boundaries in terms of variables.
After watching this video, you'd be better able to understand and appreciate how physics is so flexible as compared to the other faculties of science.
Something interesting to think about (:
Discuss on the comment section why would this happen!
Discuss on the comment section why would this happen!
Saturday, March 27, 2010
Resources
Here are a couple of web sites to explain the concepts in physics.
Some are simulation sites while others are conceptual information.
Do explore this sites for further understanding. :)
Colorado state uni physics simulations.
Projectile motion (click on the [run now!] to direct run or you can download it free)
Interscience simulation library
Simulation library (click on any link on the left to run java directly)
Some are simulation sites while others are conceptual information.
Do explore this sites for further understanding. :)
Colorado state uni physics simulations.
Projectile motion (click on the [run now!] to direct run or you can download it free)
Interscience simulation library
Simulation library (click on any link on the left to run java directly)
Tuesday, March 23, 2010
Fill in the BLANKS!
I know all of you love firing blanks! Please try this little exercise on the following link out, and check your answers on wikipedia.
Quiz
Quiz
Monday, March 22, 2010
Just a video to whet your appetite
Here's the famous footage of the Apollo 15 astronaut that dropped a hammer & feather on the moon to prove Galileo's theory that in the absence of atmosphere, objects will fall at the same rate regardless of mass.
Task:
Comment on why the 2 objects fall at the same rate even when 1 is seemingly heavier than the other. Does the same phenomenon happen on earth? What's gravity's role in this little experiment?
Greetings!
Congrats on managing to navigate yourself to this weblog. This blog would serve as a portal for you and your fellow peers to share information and experience learning collaboratively. In the weeks to come, various resources would be uploaded on this site to facilitate your learning journey. Stay tuned and be HUNGRY for more!
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