Scalar quantities: Quantities that have magnitude only. ( Speed, mass, distance)
Example:
For example speed has unit of ms^-1. but it has no direction.
Mass is kg but we don't know the direction.
Distance is 2km but no direction.
Vector quantities: Quantities that have magnitude and direction. (Velocity, Weight, Displacement)
Example:
Velocity unit is ms^-1 but we must state the direction that is whether from right to left.
Weight unit is Kg but the direction is towards the gravity pull of the earth.
Displacement is 2km but to the north from the point of reference.
Wednesday, 10 November 2010
Understanding Measurement
A micro balance is used to measure minute masses. It is sensitive but not very accurate.
Slide callipers are usually used to measure the internal or external diameter of an object.
A micrometer screw gauge is used to measure the diameter of a wire of the thickness of a thin object.
All measurement must consider this:
Accuracy: Ability of the instrument to measure the true value or close to the true value. The smaller the percentage error, the more accurate the instrument is.
Sensitivity of an instrument is the ability of the instrument to detect any small change in a measurement.
Consistency: ability of the instrument to produce consistent measurement.(the values are near to each other). The lower the relative deviation, the more consistent the measurement is.
How to increase accuracy?
- repeat the measurements and get the mean value.
- correcting for zero error.
- avoiding parallax error.
- use magnifying glass to aid in reading.
The sensitivity of a mercury thermometer can be increased by;
-having a bulb of thinner wall.
-having a capillary tube of smaller diameter or bore.
Slide callipers are usually used to measure the internal or external diameter of an object.
A micrometer screw gauge is used to measure the diameter of a wire of the thickness of a thin object.
All measurement must consider this:
Accuracy: Ability of the instrument to measure the true value or close to the true value. The smaller the percentage error, the more accurate the instrument is.
Sensitivity of an instrument is the ability of the instrument to detect any small change in a measurement.
Consistency: ability of the instrument to produce consistent measurement.(the values are near to each other). The lower the relative deviation, the more consistent the measurement is.
How to increase accuracy?
- repeat the measurements and get the mean value.
- correcting for zero error.
- avoiding parallax error.
- use magnifying glass to aid in reading.
The sensitivity of a mercury thermometer can be increased by;
-having a bulb of thinner wall.
-having a capillary tube of smaller diameter or bore.
Understanding Pressure
- Pressure on an area, A is the normal force, F, whish is being applied perpendicularly to the area.
- Pressure on an area, A is expressed as the normal force, F per unit area, A.
- P = (F/A)
- This SI unit for pressure is the pascal, Pa, where 1 Pa = 1 N/m2 (metre square).
- Pressure is increased: if the force, F applied to a given area, A is increased and if a given force, F is applied to a smaller area, A.
- If a balloon is pressed against by a finger, the balloon will only change its shape a bit. If the balloon is pushed against by a needle with the same force, the balloon will burst. This is because a finger has a larger surface area (A) than a needle. Hence, the needle exerts much pressure than the finger and perforates through the surface of the balloon and making a hole and freeing the air inside the balloon.
Thursday, 23 September 2010
The Importance of Speed and Velocity in sports.
The Best Explanation from Grade 7 students
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Written by : Brigitta, Kevin Dwi, Raissa [7a]Speed and velocity is very important and need to be included in sports. They have many useful benefits that many people need in sport. For instance, as an example, we need to know our speed and velocity in running and control it so we will not get exhausted quickly. If people can control their speed, they will not have really large amount in energy.
Speed and velocity is also needed in sports such as baseball. We need to know speed and velocity in baseball to predict when the ball will arrive (speed of the ball) and the direction too. This skill is very needed for the batter so that he or she can predict the right time, the strength and the direction when hitting the ball. This is why speed and velocity is very important.
Speed and velocity is also needed in sports such as baseball. We need to know speed and velocity in baseball to predict when the ball will arrive (speed of the ball) and the direction too. This skill is very needed for the batter so that he or she can predict the right time, the strength and the direction when hitting the ball. This is why speed and velocity is very important.
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Written by : Celine, Darwin, Franklin and Kevin [7b].It is important because we need skills that are connected to speed and velocity in sports. When we are playing sports like football, we need to pass the ball, run, we need power and that is connected to speed and velocity. When we want to pass the ball, we need speed and velocity so no one will keep up with you and results that no one will block your passing. When we are running, we can know the speed and velocity we are running and without speed, you will totally lose. When we need power, the faster you are, the stronger you are and the stronger you are, the more possibilities of winning. We can control the speed and velocity and that helps us in sports. In conclusion, speed and velocity is really important.
In the running competition, you have to know the speed. Cyclist needs speed so that they know their speed. In a running race, you need to know that speed so that you know the winner. We need to know the velocity when we are swimming so we can defeat others. In car racing, we need to know the speed that is shown by speedometer, so we don’t drive too fast and won’t cause bad damage. We need to know the velocity of badminton ball so we can hit the ball. So, in conclusion there are so many importance of speed and velocity in Physical Education.
For example in sport such as racing car. In the car they give the speedometer to read how fast the car is running. Velocity is used to know where the car is going to. Speed is importance so we know how fast is an athlete run per minute and velocity is used to know where the athlete is running. In soccer speed is used for player to run faster in the field so the player will get the ball and velocity is used to know the player direction so we can know to whom we pass the ball.
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Written by Clarissa, William, Reyna and Belinda [7c]
In the running competition, you have to know the speed. Cyclist needs speed so that they know their speed. In a running race, you need to know that speed so that you know the winner. We need to know the velocity when we are swimming so we can defeat others. In car racing, we need to know the speed that is shown by speedometer, so we don’t drive too fast and won’t cause bad damage. We need to know the velocity of badminton ball so we can hit the ball. So, in conclusion there are so many importance of speed and velocity in Physical Education.
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Written by Hans, Tirta, Angeline, Selma [7c]
Written by Hans, Tirta, Angeline, Selma [7c]
For example in sport such as racing car. In the car they give the speedometer to read how fast the car is running. Velocity is used to know where the car is going to. Speed is importance so we know how fast is an athlete run per minute and velocity is used to know where the athlete is running. In soccer speed is used for player to run faster in the field so the player will get the ball and velocity is used to know the player direction so we can know to whom we pass the ball.
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Wednesday, 22 September 2010
How to Learn Physics
For as knowledges are now delivered, there is a kind of contract
of error between the deliverer and the receiver; for he
that delivereth knowledge desireth to deliver it in such a form
as may be best believed, and not as may be best examined;
and he that receiveth knowledge desireth rather present satisfaction
than expectant inquiry.
of error between the deliverer and the receiver; for he
that delivereth knowledge desireth to deliver it in such a form
as may be best believed, and not as may be best examined;
and he that receiveth knowledge desireth rather present satisfaction
than expectant inquiry.
[Francis Bacon]
Many students approach a science course with the idea that they can succeed by memorizing the formulas, so that when a problem is assigned on the homework or an exam, they will be able to plug numbers in to the formula and get a numerical result on their calculator.
Wrong! That’s not what learning science is about! There is a big difference between memorizing formulas and understanding concepts. To start with, different formulas may apply in different situations. One equation might represent a definition, which is always true. Another might be a very specific equation for the speed of an object sliding down an inclined plane, which would not be true if the object was a rock drifting down to the bottom of the ocean.
If you don’t work to understand physics on a conceptual level, you won’t know which formulas can be used when. Most students taking college science courses for the first time also have very little experience with interpreting the meaning of an equation. Consider the equation w = A/h relating the width of a rectangle to its height and area. A student who has not developed skill at interpretation might view this as yet another equation to memorize and plug in to when needed.
A slightly more savvy student might realize that it is simply the familiar formula A = wh in a different form. When asked whether a rectangle would have a greater or smaller width than another with the same area but a smaller height, the unsophisticated student might be at a loss, not having any numbers to plug in on a calculator. The more experienced student would know how to reason about an equation involving division — if h is smaller, and A stays the same, then w must be bigger. Often, students fail to recognize a sequence of equations as a derivation leading to a final result, so they think all the intermediate steps are equally important formulas that they should memorize.
When learning any subject at all, it is important to become as actively involved as possible, rather than trying to read through all the information quickly without thinking about it. It is a good idea to read and think about the questions posed at the end of each section of these notes as you encounter them, so that you know you have understood what you were reading.
Many students’ difficulties in physics boil down mainly to difficulties with math. Suppose you feel confident that you have enough mathematical preparation to succeed in this course, but you are having trouble with a few specific things. In some areas, the brief review given in this chapter may be sufficient, but in other areas it probably will not. Once you identify the areas of math in which you are having problems, get help in those areas. Don’t limp along through the whole course with a vague feeling of dread about something like scientific notation. The problem will not go away if you ignore it. The same applies to essential mathematical skills that you are learning in this course for the first time, such as vector addition.
Sometimes students tell me they keep trying to understand a certain topic in the book, and it just doesn’t make sense. The worst thing you can possibly do in that situation is to keep on staring at the same page. Every textbook explains certain things badly — even mine! — so the best thing to do in this situation is to look at a different book. Instead of college textbooks aimed at the same mathematical level as the course you’re taking, you may in some cases find that high school books or books at a lower math level give clearer explanations. The three books listed on the left are, in my opinion, the best introductory physics books available, although they would not be appropriate as the primary textbook for a college-level course for science majors.
Finally, when reviewing for an exam, don’t simply read back over the text and your lecture notes. Instead, try to use an active method of reviewing, for instance by discussing some of the discussion questions with another student, or doing homework problems you hadn’t done the first time.
Wrong! That’s not what learning science is about! There is a big difference between memorizing formulas and understanding concepts. To start with, different formulas may apply in different situations. One equation might represent a definition, which is always true. Another might be a very specific equation for the speed of an object sliding down an inclined plane, which would not be true if the object was a rock drifting down to the bottom of the ocean.
If you don’t work to understand physics on a conceptual level, you won’t know which formulas can be used when. Most students taking college science courses for the first time also have very little experience with interpreting the meaning of an equation. Consider the equation w = A/h relating the width of a rectangle to its height and area. A student who has not developed skill at interpretation might view this as yet another equation to memorize and plug in to when needed.
A slightly more savvy student might realize that it is simply the familiar formula A = wh in a different form. When asked whether a rectangle would have a greater or smaller width than another with the same area but a smaller height, the unsophisticated student might be at a loss, not having any numbers to plug in on a calculator. The more experienced student would know how to reason about an equation involving division — if h is smaller, and A stays the same, then w must be bigger. Often, students fail to recognize a sequence of equations as a derivation leading to a final result, so they think all the intermediate steps are equally important formulas that they should memorize.
When learning any subject at all, it is important to become as actively involved as possible, rather than trying to read through all the information quickly without thinking about it. It is a good idea to read and think about the questions posed at the end of each section of these notes as you encounter them, so that you know you have understood what you were reading.
Many students’ difficulties in physics boil down mainly to difficulties with math. Suppose you feel confident that you have enough mathematical preparation to succeed in this course, but you are having trouble with a few specific things. In some areas, the brief review given in this chapter may be sufficient, but in other areas it probably will not. Once you identify the areas of math in which you are having problems, get help in those areas. Don’t limp along through the whole course with a vague feeling of dread about something like scientific notation. The problem will not go away if you ignore it. The same applies to essential mathematical skills that you are learning in this course for the first time, such as vector addition.
Sometimes students tell me they keep trying to understand a certain topic in the book, and it just doesn’t make sense. The worst thing you can possibly do in that situation is to keep on staring at the same page. Every textbook explains certain things badly — even mine! — so the best thing to do in this situation is to look at a different book. Instead of college textbooks aimed at the same mathematical level as the course you’re taking, you may in some cases find that high school books or books at a lower math level give clearer explanations. The three books listed on the left are, in my opinion, the best introductory physics books available, although they would not be appropriate as the primary textbook for a college-level course for science majors.
Finally, when reviewing for an exam, don’t simply read back over the text and your lecture notes. Instead, try to use an active method of reviewing, for instance by discussing some of the discussion questions with another student, or doing homework problems you hadn’t done the first time.
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