Thames & Kosmos DLX, Руководство по эксперименту, Страница: 34 / 132

“Golfing” with the
ball machine
YOU WILL NEED
› The assembled ball machine
› IR remote control
› 5 AA batteries or 5 AA rechargeable batteries
› Masking tape
› Scissors
› Felt-tip pen
› Large marble (small ball)
› Stop watch, note pad, and pen
HERE’S HOW
1. Familiarize yourself with the ball machine’s controls.
2. Cut 10 equal-sized squares from the roll of masking
tape and distribute them evenly and not too close to
each other across the floor.
3. Mark one square with “Start” and number the others
from 1 to 9. Those will be the 9 “holes” of your golf
course. Place the ball at the starting square.
4. Now, your task is to use the ball machine to pass the
ball to each hole in turn. You only get a point if you hit
the hole on the first try.
5. As soon as you’ve gotten a little practice hitting the
holes, you can try playing against the clock — and
against an opponent too, of course. Use the stop watch
to keep time. Here are the rules: If you don’t hit a hole
on the first try, there’s a 5-second penalty. This will be
added to the total time measured with the stop watch.
WHAT’S HAPPENING
Your ball machine is equipped with a pushing
element. You can move it back and forth, although
for this you also need a rotating motor with the
element mounted off-center.
This kind of mechanism, sometimes known as an
eccentric, consists of a drive pulley (the yellow
gear wheel) whose center (the red anchor pin)
lies outside the shaft axis. An eccentric can be
used to convert rotational into lengthwise
movements and vice versa (see also
Experiments 6 and 13). Steam locomotive
wheels are also equipped with eccentrics.
KEYWORD: REPRODUCIBILITY
To ensure that a contest is fair, you have to be sure
that each player encounters the same conditions. In
this experiment, you achieve this by constructing an
“experimental setup” that can always be reproduced
the exact same way as in the first test run. This
reproducibility is also an important requirement in
science, by the way. An experiment must always be
able to be performed by other scientists anywhere in
the world in the exact same way that it was
performed the first time.
DID YOU KNOW?
Actual ball machines
really are used at golf
courses. Instead of being
used for hitting, though,
they are used to collect
the golf balls that players have hit on the driving
range for practice.
EXPERIMENT 4
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