Two for the physics and maths students

Lift and Floater are two further titles in Cambridge Micro Software's 80 track disc educational series. These are aimed directly at the schools market, and in this case at students of physics and maths from CSE to first-year sixth form.

Lift provides a computer model of some aspects of gravitational mechanics by simulating the change in the apparent weight of a mass on a moving spring balance.

The mass, called Mabel, and the spring balance, drawn as kitchen scales, are set in a lift shaft.

With a joystick, the user controls the direction, velocity and acceleration of the scales, pushing Mabel up the shaft, meeting her as she falls, descending with her and so on. She can leave a trail of dots behind her, the distance between the dots being proportional to her velocity, and these can be seen against a grid dividing the lift shaft into equally-spaced sections.

All in all, this is a fascinating and amusing way of demon strating Newton's Second Law (force = mass X acceleration) and other principles of motion.

Apart from the use of the joystick, which gives fine control over the movement of the scales, all user-selection is by a friendly system of highlighting.

Floater, built around the same basic design and control struc ture as Lift but concerned with weightlessness rather than weight, is less amusing than its companion.

The exciting front cover of the manual shows an astronaut in free fall, with Saturn and its moons in the background.

But the cover-designers have here pandered to a fashion for games-style hype, since the program itself displays only a square two-dimensional box and a particle, unimpeded by friction, floating freely within it.

The particle conserves linear momentum, rebounding off the walls with perfect elasticity at an angle proportional to the direction of its approach.

Left to its own devices, it will continue indefinitely in its uniform motion, but, as with Lift, changes in momentum and direction are controlled by a joystick. Again, the particle can leave a stroboscopic trail of dots behind it. and the box can be marked with a grid for the purposes of measurement.

Displacement, velocity and acceleration are continuously monitored and can be displayed numerically, as graphs, or with vectors (this time Cartesian or polar).

The motion can be frozen at any time.

The educational possibilities of Floater are certainly as wide as those of Lift, but it is likely to have a narrower appeal.

A young pupil can have fun - and learn something into the bargain - just shunting Mabel up and down her lift shaft and watching her weight change.

But apart from drawing pictures with the particle's trailing dots, these programs offer little entertainment value. Having said that, I should add that to my mind the designer of these packages, who has taken into account educational value, flexibility and entertainment in that order, has got the balance just about right.

Rather, it is the programming which leaves something to be desired.

The fact that the program is unstructured, and that the code is full of GOTOs and GOSUBs is of course something which is transparent to the general user.

But in this case it is also symptomatic of the end result. For example, when all options are implemented, user-selection in the menus slows down considerably.

The manuals for both Floater and Lift are clear, well-organ ised, and comprehensive without insulting the intelligence of the user.

Most impressively, each includes a long section for teachers which will be invaluable in the classroom.

A "system" program for adjusting the monitor and set ting up a range of common printers for screen dumps is provided with both. And the function keys can be prc-set to recall combination of display options.

At £16.50 each, you can hardly say that they are good value for money, but they should provide teachers with some good material.

Katherine Cranford