Study Physics notes on MACHINES for Secondary. Useful for revision, homework, and exam preparation in Zimbabwe.
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This is the Physics notes from 2020. It is a free notes for revision.
MACHINES
MECHANICAL SYSTEMS
WORK, ENERGY \& POWER
Work done
Work is done whenever a force makes something move.
The unit for work is the Joule (J).
1 Joule is the work done when a force of 1 Newton moves one metre i.e. $1 \mathrm{~J}=1 \mathrm{Nm}$.
Work is defined as the product of force and distance.
\[
\begin{aligned}
\text { Work done } | =\text { Force × Distance }
W | =\mathrm{f} \times \mathrm{d}
\end{aligned}
\]
Energy is the capacity/ability to do work.
The amount of energy something has is also the amount of work it can do.
Work done = Energy used
Energy used $=$ force × distance
\[
E=f \times d
\]
The unit for Energy is also the Joule (J)
1 Joule is the work done or energy used when a force of 1 Newton moves one metre i.e. $1 \mathrm{~J}=1 \mathrm{Nm}$.
Power
Power is the rate at which work is done.
Or
Power is the rate at which energy is converted from one form to another.
The unit of power is the Watt (W).
\[
1 \mathrm{~W}=1 \mathrm{~J} / \mathrm{s}
\]
\[
\begin{array}{c|c}
\text { Power }=\frac{\text { Work Done }}{\text { Time Taken }} | P=\frac{W}{t}
\text { Power }=\frac{\text { Energy used }}{\text { Time Taken }} | P=\frac{E}{t}
\end{array}
\]
Weight and Mass
Mass is the amount of matter in an object.
Weight is the pull due to gravity on an object.
The relationship between mass and weight is:
\[
\mathrm{W}=\mathrm{mg}
\]
SCIENCE MADE SIMPLE © SIMBA TIGS 2020
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