Thrust
In our fifth blog of the series, we discussed forces. As a force
is any interaction when unopposed, will change the state of the object. From the same blog we are also familiar with the concept
of net force.
When
a net force is applied in a particular direction in a small fraction of time is
termed as thrust.
Thrust is a kind of an instantaneous push,
pull or interaction. When a system pushes or accelerates mass in one direction,
there is a thrust in the opposite direction. In physics, this concept is
described in Newton’s second and third laws. Thrust can be used for many kinds
of vehicles and engines such as rockets, motorboats, and jet engines etc.
Thrust is measured in newtons in the metric system.
The concept of thrust is very popular in
the daily life of human beings. Some obvious examples are, inserting a drawing
pin in a notice board to fix the poster and hammering the nail to fix it in the
wall.
Pressure
Whenever the force is applied on any
surface, it gets distributed all over the surface. The force per unit area is
termed as pressure. Physics define it as,
Pressure
is the force applied perpendicular to the surface of an object per unit area
over which that force is distributed.
Various units are used to express
pressure. Some of these are derived from a unit of force divided by a unit of area, for example, Newton per meter square (N/m2).
The SI unit of pressure, the pascal (Pa).
From our daily life observation, we know
that all the pins, nails, sticks, or rod having a narrow pointing end get
inserted easily. Whereas, if any of the rod end is not narrow, it would be
difficult to insert it in the wall.
That narrow end always has a very small
surface area with respect to the surface area of the other object. If the
surface area of the narrow end is increased, it would not be easy for the nail
to penetrate the wall. Because the applied net force on the nail will be distributed all over the
surface of the pointing end and net force will be decreased. In physics, this
kind of divided force is termed as pressure.
It is very interesting to know that
pressure is inversely proportional to the surface area of the pointing end.
Hence, as surface area decreases, pressure increases and as surface area is
increased, pressure decreases. That’s why nails, pins, knives etc. have sharp and pointing ends and
buildings, wheels etc. have wide surface area in contact with ground. This
makes them useful for humans.
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