Saturday, March 20, 2010 10:06 PM

Corrections for Exercise 2 (Time, Rate & Speed)

♥Qn2

Average speed = 8.3m / 2.2hr
= 8.3 / 7920 m/s
= 0.001047... m/s
= 0.00105 m/s ( 3 sig. fig.)

credits to Joie Tan of 104 who highlighted the error :)

Thursday, March 18, 2010 11:39 PM

Time, Rate & Speed Notes

♥A. Time

1. Time is the duration of an event which is measured in seconds (s).

2. SI Unit: seconds (s).

3 Other measurements of time include days, hours, milliseconds, and minutes, etc.

4 Instruments commonly used to measure time include mechanical stop-watches, electronic stop-watches and hour-glass.

5 The most accurate method of time keeping is the usage of atomic clocks, where every second is equivalent to a fixed number of periods of radiation from the ground state of the Caesium 133 atom.


B. Rate

1. Rate is the expression of a specific ratio in which measurements of two physical quantities are related to each another.

2. The measurements of the two physical quantities may be of different units, e.g. m/s and m/min, OR km/min and m/min.

Conversation table
Example 1
240m/min = 4m/s

Example 2
12km/min = 12000m/min
= 200m/s

3. Conversation of rates allows us to make a fair comparison when we are using the same rates.

4. Other examples of rates would include cm/s, km/h, $/min, and kg/m2.

C. Speed

1. Speed is the measurement of Distance (m) over Time (s).

2. SI Unit: metre per second (m/s).

3. Other measurement units includes miles/h, yards/min.

4. Speed tells us how fast an object is moving, and it is a rate at which distance is covered over time.

5. As an object may not be of constant speed throughout its motion, there would be a need to calculate its average speed.

6. Average speed is the measurement of total distance travelled over total time taken.

11:32 PM

Time, Rate & Speed Exercise 2 Answer Schemes

11:31 PM

Time, Rate & Speed Exercise 1 Answer Schemes

Sunday, March 7, 2010 3:02 AM

GROUP 1 - LENGTH & MEASUREMENTS

♥ GROUP 1

Members.

♥Anthea Koh

♥MaryTreesa

♥Nicole Kessler

♥Sheerin

♥FooSuYi

We will be telling you more about Length & Measurments

• The SI unit of length is metre

  
METRE RULE




Zero error

Monday, March 1, 2010 2:57 AM

♥mass. GROUP MEMEMBERS of GROUP 3::



CHARMAINE TER(5) - LEADER (:

INSYIRAH BANU(13) - DOER (:

CLAUDIA LEONG(21) - TIMEKEEPER (:

SAMANTHA RACHEL(29) - DOER (:

VANESSA TOH(37) - OBSERVER (:



The SI UNIT for Mass is Kilograms ( KG)


COMMONLY USED APPARATUS TO MEASURE WEIGHT:


Triple Beam Balance















A triple beam balance is an accurate and reliable method of measuring mass. Most triple beam balances can measure masses up to 0.61kg.



Four-beam Pan Balance










A four-beam pan balance can measure masses up to 0.311g.





Electronic Balance





An elctronic balance can obtain readings much faster than a beam balance.





Mass is not equivalant to weight.
The difference between mass and weight is apparent when, for example:



-objects are compared in different gravitational fields, such as away from the Earth's surface. For example, on the surface of the Moon, gravity is only about one-sixth as strong as on the surface of the Earth. A one-kilogram mass is still a one-kilogram mass (as mass is an intrinsic property of the object) but the downward force due to gravity is only one-sixth of what the object would experience on Earth.



-an object is immersed in a liquid or gas. For instance, a brick weighs less when suspended in water, even though its mass is unchanged, and a helium balloon in the atmosphere appears to have negative weight, even though its mass is positive.

Weight is a force that results from the action of gravity on matter. it measures how strongly gravity pulls on that matter. THINGS THAT MEASURE WEIGHT:
















FAQ:

What is mass?


Mass is the amount of material in an object. Mass stays the same no matter what force is acting on the object. This makes mass different from weight, which depends on both the amount of mass and the amount of gravity. This means that even though our elephant weighs less on the moon, his mass stays the same.


What is the SI unit for mass?
it is (kg).



What are some commonly used units in mass?

kilograms,grams,pounds,milligrams,etc.....


d)What is a triple beam balance and how is it used?



The triple-beam balance is the instrument most frequently used to
measure the mass of an object. There are 3 ways in which the triple-beam balance
may be used to measure mass,but only 2 is here.


1. Finding mass directly: The object is placed on the pan of the balance and the
riders are moved into position on the beams until the pointer is balanced at the zero
point. The mass is determined by the positions of the riders on the beams.

2. Finding mass by difference: This procedure is most frequently used to find the
mass of a liquid in a container. The mass of the empty container is subtracted from the
combined mass of the container and the liquid.


ei)What is a spring scale?


A spring scale is a device that uses the translation of a spring by force due to weight to discover the mass of an object.


eii)How to use it?

The spring scale uses a spring attached to a hook to work. The object to be weighed is hung from the hook, which compresses the spring. The amount that the spring is compressed is read on a scale.



CREDITS:

Samantha Rachel and Insyirah Banu for doing the blog.

Claudia Leong for taking pictures for the blog.

Charmaine Ter for doing the FAQ.

Vanessa Toh for giving advice and notes for the blog.