towards an analysis of errors made by university students ... - DSpace

Usually in a concrete beam, much of the concrete
simply holds the steel reinforcement in position. It can be
used much more effectively if it is 'stressed' before being
subject to an external load. Concrete can be 'pre-stressed'in
two ways. In the first method, the concrete is poured around
stretched steel wires which are released only when the concrete
has set. The other method is to pour the concrete
around
polythene tubes. When the concrete sets, steel wires are pulled
through the tubes and stretched. This is called 'built in'
stress.
In order to save time, many builders
prefer to use
a number of prefabricated units. The use of prefabricated concrete
units has made it possible to build very rapidly.
T5P - Text number 5 - Physics
CAN LIFE EXIST ON THE PLANETS?
(Part One)
(From chapter VII of THE UNIVERSE AROUND US by SIR
JAMES JEANS,
F.R.S.)
. Actually we know of no type of astronomical body
in which the conditions can be favourable to life except planets
like our own revolving around the sun. Even these may be too
hot or too cold for life to obtain a footing. In the solar
system, for instance, it is hard to imagine life existing on
Mercury or Neptune since liquids boil on the former and freeze
hard on the
latter.
Even when all the requisite conditions are
satisfied,
will life come or will it not? We must probably discard the at