|
A
|
Acceleration and motion
If an object is at rest (not moving) and is free
to move (not fixed), an external force – a force from outside – will make
the object accelerate. This means the velocity of the object (the speed of
its movement in a given direction) will increase. Velocity is measured in
metres per second (m/s). if acceleration is constant – that is, if the rate
of acceleration remains the same – t is measured as the increase in
velocity (in metres per second) that is achieved each second. The unit of
acceleration is therefore metres per second per second – stated as metres
per second squared (m/s2).
|
|
B
|
Inertia
The greater
the mass of an object (see unit 9), the greater the external force required
to cause it to accelerate or decelerate. Resistance to acceleration or
deceleration, due to the mass of an object, is called inertia. When an
object is in motion, its resistance to deceleration, due to inertia, is often
called momentum.
|
|
C
|
Simple machines
The word machine generally
refers to an assembly which has parts to move. However, a simple machine
can be a very basic device. A simple machine is something which provides a
mechanical advantage – that is, the load generated by the machine (the
force it puts out, or output) is greater than the effort (the force put in,
or input) required to generate the load.
|
EXERCISES
|
33.1
|
Complete the article about the Titanic,
taken from a popular science magazine. Look at A and B opposite to help
you.
|
It’s been suggested that the
passenger liner Titanic wouldn’t
have sunk after colliding with an iceberg in 1912, if it had hit the
obstacle head on and damaged only the front of the ship. As history
tells, the crew tried to turn to avoid the iceberg, and 1,517 lives were
lost. But how severe would a frontal impact have been for the passengers?
The answer depends on several questions.
·
The ship tried to slow while turning. Would (1)
__________ deceleration have been more effective, allowing the ship to (2)
__________ more rapidly?
|
|
|
33.2
|
Replace the
underlined words and expressions with alternative words and expressions
from A and B opposite.
|
|
|
|
The first diagram below
illustrates how a worker is able to apply a total (1) force of 50
newtons to the corner of a nut using just his fingers. The distance from
the centre of the nut – the point around which the nut (2) turns –
and the corner of the nut is 10mm. this results in a (3) force of
leverage of 0.5 newton metres. This is insufficient to tighten the
nut properly.
|
|
|
No comments:
Post a Comment
thank you for visiting my blog and for your nice comments