Group 10(Time and Speed)

TIME

~Is the duration of an event
~S.I. unit is seconds(s) Other units include the minute(min),
the hour(h) and millisecond (ms)
~Days, weeks, months and years can also express time
~Instruments used to measure time: Watches, Clocks(Both measure time to the nearest second
but not sufficiently accurate for scientific purposes)
~To measure a short period of time, a stopwatch is used

TIME: STOPWATCH
~There are two kinds of stopwatches-Mechanical and Electronic

xxxxMECHANICAL STOPWATCHxxxxx
->has a minute scale and a second scale
->smallest division is 0.1 second

xxxxELECTRONIC STOPWATCHxxxx
~is more accurate than the mechanical stopwatch
~can measure time intervals accurate to 0.01 seconds

~can also record the time interval in hours unlike the mechanical stopwatch

Instructions on how to use the above instruments are below :)

Speed

What is speed?

Speed is...
-The rate of motion, change or activity
-The rate at which distance is covered over time

Speed, like velocity, has the dimensions of a length (AKA distance) divided by time.

So if velocity and speed are so similar, why aren't they called the same thing?

There is, of course, a difference between them. To understand this difference better, we have found some videos for you to watch and learn:

size:100%;">If you do not appreciate it, there is a more logical-sounding and more professional-sounding video for you below, but its quality is not very good.





What are the instruments used to measure speed?
They are...
-The speedometers in cars




An example of a car's speedometer
Credits: Wikipedia










-Stopwatches [both digital and mechanical]

An example of a mechanical stopwatch
Credits: Wikipedia










-Chronographs [both digital and mechanical]
An example of a mechanical chronograph Credits: Wikipedia

Yes yes they are oh so helpful but HOW DO WE USE THEM (in advance, we are sorry these are advertisements...)??

This is where our wonderful youtube videos come in!


This is how to use a mechanical watch :)



This is how to use a digital stopwatch :)



This video above explains how chronographs are used :)


So after those EXTREMELY interesting videos, let's find out more about speed and objects~

Of course, the speed of objects falling falls into the topic, so let us talk more about it!

~~~Around 400 years ago, the great scientist Galileo noticed that objects speed up when they fall. He later found out that objects of different masses but have the same shape take the same time to fall to the ground. He later found out that gravity pulls them down equally.
Objects of different shapes and sizes fall at different rates...BUT....the faster something falls, the more air resistance acts on the object. Eventually, the air resistance acting on it becomes as strong as the gravitational force acting on it. When this happens, the object's speed no longer changes and is hence called terminal speed.

There are still many words you have to read, so get some eyedrops before proceeding~!

Ready? Go!

So what about the speed of light and the some of the fastest specimens of the world?

That is what we are going to cover now!

The speed of light is 299, 792, 458 metres/second

Fastest land animal?

Hands (I mean paws) down, it's the cheetah at 110km/hour!

Speed of a racing hovercraft?

It is around 70 miles per hour! (but still slower than the cheetah)

Speed of a swordfish?

At maximum, its speed is 60km/hour~

Lastly *pants*, the hummingbird...

It can fly backwards and its maximum speed is 54km/hour!

Lastly, questions from your textbook....

-Arrange the following walking speeds of different dinosaurs in ascending order:
a. Stegosaurus 1.67m/s
b. Large theropods (e.g. tyrannosaurus) 20km/h
c. Sauropods (e.g. diploducus) 283.33m/min

Answer:
http://answersforscienceblog.blogspot.com/2010/02/q1-dinosaurs.html

[the easiest of the easy] Suppose you are standing in a platform of an MRT station watching the trains. There is a train passing by without stopping. It travels at 20m/s and takes 6.9s to completely pass you. What is the length of the train?

Answer:
http://answersforscienceblog.blogspot.com/2010/02/q2-train.html

We hope you have enjoyed our post!
Group members: Therese, Charmaine (Time), Rachel Lo and Priscilla (Speed) :D