### Why do this problem?

This

problem gives an interesting exploration into ideas concerning
power and weight. It encourages accurate manipulation of numbers
and units without requiring too much technical mathematics. As
such, it is great for devloping numerical intuition about power.

### Possible approach

There are various parts to this question which may be
considered independently. At various points, changes of units will
be necessary, and part of the problem is to keep track of which
units are required. There is an emphasis on numerical accuracy and
manipulation, and the correct numerical results are interesting and
worth discussion: at each stage ask: what do these numbers tell us?
why are they interesting? is this number large, small,. surprising?
how does this compare to another object that I know about? For
example, the power to weight ratio of a cart horse is about 1,
making it easy to work out the horsepower of various more powerful
machines.

### Key questions

How does application of power change the energy of the
system?

How many miles in a kilometre, feet in a centimetre, seconds
in an hour, pounds in a kilogram?

### Possible extension

The extension investigation task included in the problem will
yield many interesting avenues of thought

### Possible support

The hint offers a good way in to the question.