It looks something like this .First , we had to measure the length of the string , from the center of the pendulum to the base of the cock.
One Period of oscillation is the time it takes the pendulum to travel the arc ABC . One beat is equal to half the period of oscillation or the time it takes the pendulum to travel the arc AB or BC
We had to time one oscillation of the pendulum , we had to do that step 3 times so the results would be accurate .
Then We were given a plasticine to wrap the pendulum , to find out if the weight of the pendulum increased , will the oscillation of the pendulum be shorter . We then had to draw a table to record all the readings down , then take the average and find one period of the pendulum . I did not fill in that part , then i handed it up since i did not know how to do , but now , although im not sure if this is the correct method , to find the period of the pendulum , take the average time of 10 oscillations and divide it by 10 .
Osmium
Osmium (Greek osme meaning "smell") was discovered in 1803 by Smithson Tennant and William Hyde Wollaston in London, England.[1] The discovery of osmium is intertwined with that of platinum and the other metals of the platinum .
Osmium is generally considered to be the densest known element, narrowly defeating iridium . However, calculations of density from the space lattice may produce more reliable data for these elements than actual measurements and give a density of 22650 kg/m3 for iridium versus 22610 kg/m³ for osmium. Definitive selection between the two is therefore not possible at this time. If one distinguishes different isotopes, then the highest density ordinary substance would be 192Os. The extraordinary density of osmium is a consequence of the lanthanide contraction.
Iridium
Iridium was discovered in 1803 by Smithson Tennant among insoluble impurities in natural platinum from South America. It is one of the rarest elements in the Earth's crust, with annual production and consumption of only three tonnes. However, iridium does find a number of specialized industrial and scientific applications. Iridium is employed when high corrosion resistance and high temperatures are needed, as in spark plugs, crucibles for recrystallization of semiconductors at high temperatures, electrodes for the production of chlorine in the chloralkali process, and radioisotope thermoelectric generators used in unmanned spacecraft. Iridium compounds also find applications as catalysts for the production of acetic acid. One of the lesser-known members of the platinum group metals, iridium is white, resembling platinum, but with a slight yellowish cast. It possesses quite remarkable chemical and physical properties.
The Iridium has a density of 22650 kg/m3.
As the information states that the two elements are about of the same density , but i think that Osmium should be denser ...
A free falling object achieves its terminal velocity when the downward force of gravity (Fg) equals the upward force of drag (Fd). This causes the net force on the object to be zero, resulting in an acceleration of zero. Mathematically an object asymptotically approaches and can never reach its terminal velocity.As the object accelerates (usually downwards due to gravity), the drag force acting on the object increases. At a particular speed, the drag force produced will equal the object's weight (mg). Eventually, it plummets at a constant speed called terminal velocity (also called settling velocity). Terminal velocity varies directly with the ratio of drag to weight. More drag means a lower terminal velocity, while increased weight means a higher terminal velocity. An object moving downward with greater than terminal velocity (for example because it was affected by a downward force or it fell from a thinner part of the atmosphere or it changed shape) will slow until it reaches terminal velocity.
Based on wind resistance, for example, the terminal velocity of a skydiver in a free-fall position with a semi-closed parachute is about 195 km/h (120 mph or 55m/s). This velocity is the asymptotic limiting value of the acceleration process, since the effective forces on the body more and more closely balance each other as the terminal velocity is approached. In this example, a speed of 50% of terminal velocity is reached after only about 3 seconds, while it takes 8 seconds to reach 90%, 15 seconds to reach 99% and so on. Higher speeds can be attained if the skydiver pulls in his limbs (see also freeflying). In this case, the terminal velocity increases to about 320 km/h (200 mph or 90 m/s), which is also the terminal velocity of the peregrine falcon diving down on its prey. And the same terminal velocity is reached for a typical 150 grain bullet travelling in the downward vertical direction — when it is returning to earth having been fired upwards, or perhaps just dropped from a tower — according to a 1920 U.S. Army Ordnance study.
When referring to Sophia's blog , she posted this very interesting videos on terminal velocity , if you want , you can go view her blog :D
Source taken from : http://en.wikipedia.org/wiki/Terminal_velocity
Archimedes' father was Phidias, an astronomer. We know nothing else about Phidias other than this one fact and we only know this since Archimedes gives us this information in one of his works, The Sandreckoner. A friend of Archimedes called Heracleides wrote a biography of him but sadly this work is lost. How our knowledge of Archimedes would be transformed if this lost work were ever found, or even extracts found in the writing of others.
The Archimedes screw can raise water efficiently can raise water efficientlyArchimedes was a native of Syracuse, Sicily. It is reported by some authors that he visited Egypt and there invented a device now known as Archimedes screw. This is a pump, still used in many parts of the world. It is highly likely that, when he was a young man, Archimedes studied with the successors of Euclid in Alexandria. Certainly he was completely familiar with the mathematics developed there, but what makes this conjecture much more certain, he knew personally the mathematicians working there and he sent his results to Alexandria with personal messages. He regarded Conon of Samos one of the mathematicians at Alexandria, both very highly for his abilities as a mathematician and he also regarded him as a close friend.
How he died
Archimedes died during the Siege of Syracuse when he was killed by a Roman soldier despite orders that he should not be harmed. Cicero describes visiting the tomb of Archimedes, which was surmounted by a sphere inscribed within a cylinder. Archimedes had proven that the sphere has two thirds of the volume and surface area of the cylinder (including the bases of the latter), and regarded this as the greatest of his mathematical achievements.
Shuttles are equipped with vacuum toilets that work a little like a vacuum cleaner
Water cannot be used in the weightless environment of space so, like wash basins, toilets on the space shuttle can't use water. In a corner of the shuttle's mid-deck there is a toilet for use by both men and women. Although it looks like any other toilet used on Earth, it is a little different. To make sure what goes into the toilet doesn't come out, it is sucked away and then vacuum-dried. The system is a little different depending on whether the astronaut urinates or defecates. When urinating, the waste is sucked away in a hose. But when defecating, the toilet is used the same way as a normal toilet and the astronaut pulls a lever to have the waste sucked away. In the past, astronauts had to use bags instead of toilets and they needed considerable toilet training
Space Shuttle toilets are said to be a little difficult to use and require some practice. But even so, this is a big improvement on the past. For the first astronauts, whose stays in space were all short-term, the astronauts all wore diapers and their waste was collected in bags and taken back to Earth. Most astronauts were more than a little unhappy with this situation. Unlike on Earth, pushing alone does not allow the astronauts to defecate. Even when they do manage to get something out in a weightless environment, it often flies around the ship, gets stuck on bodies and other parts of the shuttle, or simply floats, meaning that astronauts need to have quite a bit of training before they are capable of using shuttle toilets. But even now, during take-off, re-entry or during a space walk, astronauts must wear pressurized suits and can't use the toilet, meaning they must wear either diapers or have a bag to catch their waste.
When an astronaut pees, where does it go?
Send it back to Earth or eject it into outer space . Space toilets separate solid and liquid waste, and the solid waste is tightly bagged until it can be removed. On a space shuttle, solid waste is compressed, stored, and then brought back to Earth. The space station, on the other hand, deposits the solid waste onto an unmanned vehicle (known as a"Progress Module") that is eventually released toward Earth, burning up on its re-entry into the atmosphere .
Watch this video , its about an astronaut explaining about how astronauts relieve themselves in space , its really funny .
References taken from : http://www.theplumber.com/toiletsinspace.html , http://www.slate.com/id/2192383/
Liquefaction is a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or other rapid loading. Liquefaction and related phenomena have been responsible for tremendous amounts of damage in historical earthquakes around the world. Liquefaction occurs in saturated soils, that is, soils in which the space between individual particles is completely filled with water. This water exerts a pressure on the soil particles that influences how tightly the particles themselves are pressed together. Prior to an earthquake, the water pressure is relatively low. However, earthquake shaking can cause the water pressure to increase to the point where the soil particles can readily move with respect to each other.
When has liquefaction occurred in the past ?
Liquefaction has been observed in earthquakes for many years. In fact, written records dating back hundreds and even thousands of years describe earthquake effects that are now known to be associated with liquefaction. Nevertheless, liquefaction has been so widespread in a number of recent earthquakes that it is often associated with them. Examples of earthquake :
Where does liquefaction often occur ?
To understand liquefaction, it is important to recognize the conditions that exist in a soil deposit before an earthquake. A soil deposit consists of an assemblage of individual soil particles. If we look closely at these particles, we can see that each particle is in contact with a number of neighboring particles. The weight of the overlying soil particles produce contact forces between the particles - these forces hold individual particles in place and give the soil its strength.
 Soil grains in a soil deposit. The height of the blue column to the right represents the level of porewater pressure in the soil. 
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water pressure. In an extreme case, the porewater pressure may become so high that many of the soil particles lose contact with each other. In such cases, the soil will have very little strength, and will behave more like a liquid than a solid - hence, the name "liquefaction".What is a quick sand ? How do you escape from a quick sand ?
Quicksand is actually solid ground that has been liquefied by a saturation of water. Quicksand is not a unique type of soil; it is usually just sand or another type of grainy soil. Quicksand is nothing more than a soupy mixture of sand and water. It can occur anywhere under the right conditions.Quicksand is created when water saturates an area of loose sand and the ordinary sand is agitated. When the water trapped in the batch of sand can't escape, it creates liquefied soil that can no longer support weight. There are two ways in which sand can become agitated enough to create quicksand:
- Flowing underground water - The force of the upward water flow opposes the force of gravity, causing the granules of sand to be more buoyant.
- Earthquake - The force of the shaking ground can increase the pressure of shallow groundwater, which liquefies sand and silt deposits. The liquefied surface loses strength, causing buildings or other objects on that surface to sink or fall over.
Quicksand forms when uprising water reduces the friction
between sand particles, causing the sand to become "quick."
As long as it’s left alone, the structure remains stable. But as soon as it’s disturbed, by stepping on it, the clay changes from a jelly-like consistency to a runny liquid. The effect is the same as stirring a pot of yoghurt. Liquefying the clay makes the quicksand about one million times runnier, and the whole house of cards comes tumbling down, with you inside it.
Very quickly, the sand sinks to the bottom and the water floats to the top. This is where the salt comes in. When there’s enough salt present, as soon as the clay particles liquefy, electrical charges make them begin to stick together to form bigger particles and these also settle with the sand.
The result is a very stodgy layer of sand and clay, which is twice as dense as the original quicksand and packed tightly around the trapped body parts.
While quicksand can occur in almost any location where water is present, there are certain locations where it's more prevalent. Places where quicksand is most likely to occur include:
- Riverbanks
- Beaches
- Lake shorelines
- Near underground springs
- Marshes
How do you escape from a quicksand ?
The human body has a density of 62.4 pounds per cubic foot (1 g/cm3) and is able to float on water. Quicksand is denser than water -- it has a density of about 125 pounds per cubic foot (2 g/cm3) -- which means you can float more easily on quicksand than on water. The key is to not panic. Most people who drown in quicksand, or any liquid for that matter, are usually those who panic and begin flailing their arms and legs.
If you step into quicksand, it won't suck you down. However, your movements will cause you to dig yourself deeper into it. With quicksand, the more you struggle in it the faster you will sink. If you just relax, your body will float in it because your body is less dense than the quicksand. Try spreading your arms and legs far apart and leaning over to increase your surface area, which should allow you to float.
Reference taken from: http://science.howstuffworks.com/quicksand1.htm , http://science.howstuffworks.com/quicksand2.htm , http://www.thenakedscientists.com/HTML/articles/article/whatisquicksand-1/
Newton's first law states that every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force. This is normally taken as the definition of inertia. The key point here is that if there is no net force acting on an object (if all the external forces cancel each other out) then the object will maintain a constant velocity. If that velocity is zero, then the object remains at rest. If an external force is applied, the velocity will change because of the force.
The second law explains how the velocity of an object changes when it is subjected to an external force. The law defines a force to be equal to change in momentum (mass times velocity) per change in time. Newton also developed the calculus of mathematics, and the "changes" expressed in the second law are most accurately defined in differential forms. (Calculus can also be used to determine the velocity and location variations experienced by an object subjected to an external force.) For an object with a constant mass m, the second law states that the force F is the product of an object's mass and its acceleration a:
F = ma
Force=mass acceleration
For an external applied force, the change in velocity depends on the mass of the object. A force will cause a change in velocity; and likewise, a change in velocity will generate a force. The equation works both ways.
The third law states that for every action (force) in nature there is an equal and opposite reaction. In other words, if object A exerts a force on object B, then object B also exerts an equal force on object A. Notice that the forces are exerted on different objects. The third law can be used to explain the generation of lift by a wing and the production of thrust by a jet engine.
reference taken from:http://www.grc.nasa.gov/WWW/K-12/airplane/newton.html
What is a meniscus?
A meniscus is what happens when you put a liquid into a container. When you put water in a beaker or test tube, you see a curved surface. With most liquids, the attractive force between the liquid and the container is greater than the attraction between the individual liquid molecules. So the liquid "sticks" to the side of the container.
In order to read the test tube, you have to read the "bottom" of the meniscus .So, you have to hold the tube up level with your eye, and look through it to see the bottom part of the meniscus. This takes a little practice, and you have to estimate a little. But if you always use the same method, and read from the bottom of the meniscus, you will have a constant way of doing it. That will help reduce errors in your experiments.
A: The bottom of a concave meniscus.
B: The top of a convex meniscus.
A convex meniscus occurs when the molecules have a stronger attraction to each other than to the container.
A concave meniscus occurs when the molecules of the liquid attract those of the container.
Taken from :http://education.jlab.org/qa/meniscus_01.html and http://en.wikipedia.org/wiki/Meniscus
The Greenwich Meirdian (Prime Meridian or Longitude Zero degrees) marks the starting point of every time zone in the World. GMT is Greenwich Mean (or Meridian) Time is the mean (average) time that the earth takes to rotate from noon-to-noon.
GMT is World Time and the basis of every world time zone which sets the time of day and is at the centre of the time zone map. GMT sets current time or official time around the globe. Most time changes are measured by GMT. Although GMT has been replaced by atomic time (UTC) it is still widely regarded as the correct time for every international time zone.
taken from : http://wwp.greenwichmeantime.com/what-is-gmt.htm
Density = Ag/cm³Density of solid = Ag/cm³
Ans:The solid will be in the middle of the beaker , if the density of the solid is lower , the solid will float , if the density of the solid is higher , it will sink . As the density of both are the same , the solid will be in the middle .
Why do you need to take the average ?
It is to ensure that the experiment is accurate .
Volume-->cubic metres
Mass divide by Volume = Density
Density--> kg/cubic metres
100cm = 1m
100cm x 100cm = 10,00 sq cm
1m x 1m = 1 sq metre
1millisecond = 0.01 second .
Weight is measured in [N] Newtons . Example of instrument that can measure weight is the spring balance .
Mass
Mass is measured in [kg] kilograms . Example of instrument that can measure mass is the beam balance .
1kg=10 Newtons
The gravitational pull on the Moon is 1.6N/kg
Topic 5:
A submarine can float on a water surface. It can also cruise below the surface. What special structure of the submarine allows it to operate this way? Explain.
There are ballast tanks on the side of the submarine . In order to sink , the ballast tanks lets out some air and take in water , as water has weight , the submarine will sink . In order for the submarine to float , the ballast tanks pump in air resulting in pushing some water out , with less weight , the submarine will float .
Food for thought :
If a submarine lands on the seabed, why is it unable to move and float again once more?
Ans :
The submarine moves forward with an outward thrust , when the submarine lands on the seabed , the outward thrust is gone , hence it can no longer move . Even if it moves , it would not be able to float up anymore .
it unable to float back up?
Feel free to leave comments for my previous posts :D
Topic 4: A beam balance will give you a different mass reading on the moon from that on Earth. A beam balance, however, will give you the same reading. Explain why.
The picture above is a picture of a spring balance . The spring balance measures weight in Newtons . The spring balance measures WEIGHT by the gravitational pull from the earth , since the gravitational pull on earth and the moon is different , the weight measured by the spring balance would also be different .
The picture above is a picture of a beam balance . Unlike the spring balance , the beam balance measures MASS and mass is constant . The beam balance does not depend on the gravitational pull from the earth , therefore , the beam balance will give you the same reading on earth and on the moon .
Topic 3:
In a production line, 10,000 small screws are to be sorted into packs of 50 each. Manual counting would be too tedious. Suggest ways in which the sorting may be done quickly.
Solutions :
1.Adjust the resistance of the electromagnet such that it will attract 50 screws .
But this cannot be done as we cannot exactly adjust the resistance level of the screws . If we just adjust it to a specific resistance level , it will either attract all or none of the screws .
2.Count 50 screws and place them on the weighing scale. Record the weight down. Take a pile of screws and place them on the weighing scale. Take away of add screws according to the weight of the second pile.
You are given a length of copper wire with a small diameter. The only instrument available ot you is the metre ruler. Explain how you would measure the diameter of the wire with an acceptable degree of accuracy.
Solution:
l = nd
l --length of coiled wire
n --number of turns
d --*diameter
*The thickness of the wire is its diameter
Example:
There are 4 turns. The length of the coiled wire is 4 cm.
4 cm = 4 d
d = 1cm
radius : 125cm
*NOTE: 1ml = 1cm (http://www.unitconverters.net/)
This is the method taught , there is another method , the ticking method , but if you compare the method taught to the ticking method , the ticking method would be too tedious . So , the method taught would be much easier :D
