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Thursday 20 March 2014

Measuring Equipments

This Post was not meant to be posted today. This lesson was conducted a few weeks ago...

We all know the measuring tape and the measuring rule. We, in fact, know how to use them. Here is the picture of the two.
Measuring Tape
Measuring Ruler
However, the lesson was meant to teach about the usage of the Vernier Caliper, and the Micrometer Screw Gauge.
Vernier Caliper
Micrometer Screw Gauge
Let us compare the range of measurement, and the precision (A metre rule is used instead of a measuring rule):

Instrument                         | Range of Measurement | Precision
Measuring Tape                | 0 - 5 m                         | 0.1 cm
Metre Rule                        | 0 - 1 m                        | 0.1 cm
Vernier Caliper                  | 0 - 15 cm                    | 0.01 cm
Micrometer Screw Gauge  | 0 - 2.5 cm                   | 0.001 cm (0.01 mm)

The Vernier Caliper allows the measurement of 3 different types of measurement: The External Caliper for the External Diameter; the Internal Caliper for the Internal Diameter; and the Depth Probe to measure Depth. They are represented by 1, 2, and 3 on the digram respectively.

How do you read a Vernier Caliper? This 5 minute video will teach you in detail how to use it.
This Java Applet lets you try out the vernier caliper online. (Note: Clicking on close simulation will close the webpage.)


The Micrometer Screw Gauge, on the other hand, measures in millimetres. It is usually used to measure diameter.  The method to read is shown in the two minute video below.


Though they can measure precisely, they have problems in terms of zero error. For the Micrometer Screw Gauge, zero error occurs when the zero marks on the thimble scale and the datum failed to align the thimble and anvil to meet. For the Vernier Caliper, zero error occurs when the two jaws on the vernier scale and the main scale failed to align when the jaws are completely closed.

Examples of Zero Error are as follows:

Negative Zero Error for Vernier Caliper

Positive Zero Error for Vernier Caliper
The above are zero errors for the Vernier Caliper. The 0 on the Vernier scale and Main Scale is supposed to be aligned, but it is not. The Zero Error for both are -0.08 cm and 0.08 cm each. When we are making the calculations, remember to deduct the zero error.

For the Micrometer Screw Gauge, the below photo shows the difference between no zero error, positive zero error, and negative zero error.


For this, the Positive Zero Error is 0.02mm while for the negative, it is -0.04mm.

Now, let us talk about the Ticker-Tape Timer. The information below is based on personal research, as I was only know the brief idea of this machine. This machine is better than the stopwatch, as it eliminates the problem of human reaction time. However, this timer can only be used in limited locations, and it requires some time for the data to be processed and for the actual time to be calculated.

Here is a video on the Ticker-Tape Timer:


The Ticker-Tape is attached to a machine. This machine will make the dots.

Between two consecutive dots there is a time interval of 1/50 s or 0.02 s. If there are 10 spaces on a piece of tape, the time taken for the tape to pass through will be
10 x 0.02 s = 0.20 s. 
This section of the tape is also known as a 10-dot tape. Note that the counting starts from zero.

A 10-dot Tape

Monday 17 March 2014

Newton's The Three Laws of Motion

Newton created three laws of motion. Newton's laws of motion are three physical laws that together laid the foundation for classical mechanics. They describe the relationship between a body and the forces acting upon it, and its motion in response to said forces. The three laws, though expressed differently, can be summarised as follows:


  1. Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.
  2. The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma. Acceleration and force are vectors in this law the direction of the force vector is the same as the direction of the acceleration vector.
  3. For every action there is an equal and opposite reaction.

The first law is famously known as the law of inertia, which explains how something cannot start or stop moving, increase or decrease its speed, or change directions without another force.
The first law of motion
An object continues to do whatever it happens to be doing unless a force is exerted upon it. If it is at rest, it continues in a state of rest. This is demonstrated when a tablecloth is whipped from under dishes on a tabletop and the dishes remain in their initial state of rest. If an object is moving, it continues to move without turning or changing its speed. This is evident in space probes that continually move in outer space. Changes in motion must be imposed against the tendency of an object to retain its state of motion. In the absence of net forces, a moving object tends to move along a straight line path indefinitely.


The Second Law of Motion
The second law says that the acceleration of an object produced by a net applied force is directly related to the magnitude of the force, the same direction as the force, and inversely related to the mass of the object. This shows that although one exerts the same amount of force on two different objects, the acceleration might be different. The acceleration on the smaller mass will be greater, for example, the effect of a 10 newton force on a baseball would be much greater than that same force acting on a truck. The difference in effect (acceleration) is entirely due to the difference in their masses.

The third laws says that forces are found in pairs. Think about the time you sit in a chair. Your body exerts a force downward and that chair needs to exert an equal force upward or the chair will collapse. The gravity is the force pulling it down, while there is an upward force that keeps you on the chair. Acting forces encounter other forces in the opposite direction.

Saturday 15 March 2014

Mass, Weight and Density

Mass. Everyone knows what is mass. Everyone has a mass. However, do everyone know the difference between mass and weight?

No. People tend to say, "My weight is 50 kg." Same here. Before I learnt about this, I also make this mistake. In fact, I used to think that the were synonymous!

What about density? Not many know the word density, but about the idea behind density. For example, why do some things float on water while some sink in water? This is partially due to density.


Firstly, let me explain this three terms scientifically. Mass is the amount of matter inside any object. Mass is referring to the amount of matter packed in the object. The SI Unit of Mass is Kilograms (kg). Weight is the pull of gravity on the mass. Weight's SI Unit is Newton (N). So the difference? Mass is a scalar quantity, while Weight is a Vector quantity. (Scalar and Vector Quantity will be explained in the future blog post) Mass is a base quantity, while Weight is a derived quantity.


Mass times Acceleration
Equation of Weight
Density, also known as ρ, is also a derived quantity. It is defined as the mass of a substance per unit volume. An object that is denser if it has a greater amount of matter packed into the same volume compared to that of another object. Though the SI Unit is kg per meter cube, a common unit is gram per centimeter cube.

Tuesday 4 March 2014

The Scientific Method

Note: This lesson was conducted on the 8th January 2014

We learnt about the Scientific Method. The Scientific Method is used by researchers to support or disprove a theory. This method helps to answer questions that are scientific.

The Scientific method involves the following steps:
  1. Observation - You observe something using senses.
  2. Question - You ask a question on what you observe.
  3. Hypothesis - You predict what you think the answer might be.
  4. Method - You figure out a way to test whether your hypothesis is correct. Make sure that the result is quantifiable.
  5. Result - You do the experiment using the method you cane up with and record the results. Repeat the experiment to confirm the results.
  6. Conclusion - You state whether your prediction was confirmed or not and explain it. 

Sometimes, if the hypothesis is wrong, you need to repeat the entire method all over again. This is very useful when doing the experiments.

Sunday 2 March 2014

Units

Note: This lesson was completed on the 11th and the 18th February.

Units. There are tons and billions of units in the world. Who doesn't know that? For mass, we have grams (g), kilograms (kg), Metric tonne (t), pound (Ib), Ounces (oz), Stones (st), etc. For length, we have Centimetres (cm), Feet (ft), Inches (In), Kilometres (km), miles (mi), Nautical miles (nmi), Yards (yd), etc. For Temperature, we have Celsius (°C), Fahrenheit (°F) and Kevin (K). There are tons and tons of it. However, what happens when there is no standard unit? There must be a standard unit around the world!

The International System of Units, also known as the SI units, was invented in the 1960. The SI Units consist of SI base units, and the SI derived units.

The SI basic units are as below:

SI Base Units
The SI Base Units usually do not have a prefix, with the exception being kilo in kg. 
The SI derived units shows how it is derived from SI base units, as shown below:

SI Derived Units

Saturday 1 March 2014

Observation Vs Inference

Note: This Lesson was completed on the 29th January.


At the lab, we tested our observations with a series of experiment. The Experiments are as follows:

Firstly, To add Sodium Bicarbonate to Vinegar, or chemically, add NaHCO3 to C2H4O2. 
Next, add Sodium Carbonate and Copper Sulfate respectively to Water.
Thirdly, Use a dropper to place one drop of Methylated Spirits onto the back of our hand and blow air gently across.
Fourth, Blow Carbon Dioxide to Limewater.
Fifth, Add Iodine to Starch.

The observations was as follows:

For the First, the Sodium bicarbonate dissolved to form a colourless solution. Effervesence of a colour less and odourless gas was seen.
Two: The Sodium Carbonate dissolved to form a clolourless solution. So the the Copper Sulfate, but instead blue precipitate was formed.
Three: There was a cooling sensation.
Four: White Percipitate was formed.
Fifth: It turned Blue Black.

Below are some photos in the experiment.
Empty test Tube
The Four Substances Required for Experiment 1 & 2
Copper sulfate and Water Mixture
The Three Test Tube Mixtures of:
Sodium Bicarbonate + Vinegar
Sodium Carbonate + Water
Copper Sulfate + Water

Lime Water
Blowing into the lime water
The result of  Limewater and Carbon dioxide
Starch and Iodine

Iodine, Starch, and the Mixture in Between

Another observation test we did was with this video.
See how many observations can you  make!



On average, we did 15 to 19 observations, though the highest was 25 to 30, the mode was 20 to 24, and 2 people completed the lowest range of 5 to 9. Personally, I did 18, and I was really surprised that some guy could do 25 to 30 observations.