# 0.2 Tg physical science - chapter contexts  (Page 7/10)

 Page 7 / 10

Refer to the chapter on units. By showing that the units $\mathrm{kg}·m·{s}^{-2}$ are equal to J, and mixing units and energy calculations will assist learners to be more watchful when solving problems to convert given data to SI base quantities and units.

Kinetic energy is the energy an object has because of its motion. The kinetic energy of an object can be determined by using the equation:

${E}_{k}=\frac{1}{2}{\mathrm{mv}}^{2}$

In words, mechanical energy is defined as the sum of the gravitational potential energy and the kinetic energy, and as an equation:

${E}_{M}={E}_{P}+{E}_{K}=\mathrm{mgh}+\frac{1}{2}{\mathrm{mv}}^{2}$

Both the laws of conservation of energy and conservation of mechanical energy are states. To solve problems the latter is applied in the form:

$\begin{array}{}{U}_{\mathrm{top}}={U}_{\mathrm{bottom}}\\ {E}_{P\mathrm{top}}+{E}_{K\mathrm{top}}={E}_{P\mathrm{bottom}}+{E}_{K\mathrm{bottom}}\end{array}$

To assess their degree of understanding of the content and concepts, learners are advised to engage in studying the worked examples and do the set problems.

## Transverse pulses

Transverse pulses on a string or spring are discussed, but first the questions are asked: What is a medium? What is a pulse? The following terms related to transverse pulse are introduced, defined and explained: position of rest, pulse length, amplitude and pulse speed. When a transverse pulse moves through the medium, the particles in the medium only move up and down. This important concept is illustrated by a position vs. time graph. When learners engage in doing the investigation, drawing a velocity-time graph and studying the worked example, they will get to grips with the concepts. When two or more pulses pass through the same medium at the same time, it results in constructive or destructive interference. This phenomenon is explained by superposition, the addition of amplitudes of pulses.

## Transverse waves

A transverse wave is a wave where the movement of the particles of the medium is perpendicular to the direction of propagation of the wave. Concepts addressed include: wavelength, amplitude, frequency, period, crests, troughs, points in phase and points out of phase, the relationship between frequency and period, i.e. $f=\frac{1}{T}$ and $T=\frac{1}{f}$ , the speed equation, $v=f\lambda$ .

## Longitudinal waves

In a longitudinal wave, the particles in the medium move parallel to the direction in which the wave moves. It is explained how to generate a longitudinal wave in a spring. While transverse waves have peaks and troughs, longitudinal waves have compressions and rarefactions. A compression and a rarefaction is defined, explained and illustrated. Similar to the case of transverse waves, the concepts wavelength, frequency, amplitude, period and wave speed are developed for longitudinal waves. Graphs of particle position, displacement, velocity and acceleration as a function of time are presented. Problems set on the equation of wave speed for longitudinal waves, $v=f\lambda$ , concludes this section.

## Sound waves

Sound is a longitudinal wave. The basic properties of sound are: pitch, loudness and tone. Illustrations are used to explain the difference between a low and a high pitch and a soft and a loud sound. The speed of sound depends on the medium the sound is travelling in. Sound travels faster in solids than in liquids, and faster in liquids than in gases. The speed of sound in air, at sea level, at a temperature of formula ${21}^{°}C$ and under normal atmospheric conditions, is $344m·{s}^{-1}$ . Frequencies from 20 to 20 000 Hz is audible to the human ear. Any sound with a frequency below 20 Hz is known as an infrasound and any sound with a frequency above 20 000 Hz is known as an ultrasound.

#### Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
why we need to study biomolecules, molecular biology in nanotechnology?
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
why?
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
what does nano mean?
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
for screen printed electrodes ?
SUYASH
What is lattice structure?
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
how did you get the value of 2000N.What calculations are needed to arrive at it
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