Quercetti Skyrail 6635, Instruction Manual

Page: 20 / 32

object. For example a boulder is very heavy because
there is a lot of compact material in it; however a balloon
of the same size has much less material in it (mostly air)
so is very light. Let’s now examine the marbles supplied
with Skyrail Suspension: the small steel marbles are the
ones with more mass so are the heaviest. The glow-in-
the-dark marbles on the contrary are much lighter even
if they are quite larger, because made of plastic. So you
are beginning to understand that gravity is a force that
acts on marbles during their run and has effects on their
speed, accelerating or decelerating them according to
the slope: the longer the slope the more time gravity has
to exert its power.
CENTRIFUGAL FORCE: is
the force that makes mar-
bles go out of the turns
when they are too fast or
makes them go around a
loop instead of falling down
in the middle of it. This hap-
pens because any object
tends to maintain the same straight direction if there are no
other forces to make it change its path. So, since there are
no guard-rails along the turns of Skyrail Suspension, mar-
bles tend to keep going straight if they have enough
speed. The only force that can
contrast this straight motion is
gravity that pushes the mar-
bles down against the rails.
You can experiment what is
the maximum speed that each
type of marble can travel to
remain inside the rails and go
around the turn. You can regu-
late the arriving speed of mar-
bles to the turns by adjusting
the length of cables. You will discover that the steel mar-
ble is the one that can travel along the turn at higher
speed. By now you should intuit why: it has more mass so
gravity keeps it more “attached” to the rails; and it’s smal-
ler so the external rail makes more resistance to its ten-
dency to exit.
KINETIC ENERGY:
assemble the tracks
in such way to have
a descent and then
an ascent of exactly
the same inclination and length. Then drop two marbles
exactly in the same moment from the two tops in opposite
directions. This is a very interesting and fun experiment
that will allow you to understand better concepts like
MASS and KINETIC ENERGY. Kinetic Energy is the
energy an object accumulates in itself because of its mass
and of its movement (from the Greek “Kinesys”). Let’s see
what can happen to the marbles: 1) If you drop two mar-
bles of the same type (same material, size and weight)
they will crash at the bottom of the track, right in the midd-
le between the two climbs, and stop each other instantly,
bouncing back slightly. Why? Because they have stored
the same amount of kinetic energy: during the collision this
energy is transferred from one marble to the other, and
makes the marbles stop on the spot. 2) If you change the
dropping point of one of the 2 marbles you will see that the
marble starting higher will push backward the marble star-
ting lower. Why? Because the higher marble has reached
a higher speed and so has stored more kinetic energy that
passing to the slower marble makes it move backward for
quite a distance. 3) Now drop 2 different types of marbles
from the same height, for example a steel marble and a
glass marble. What happens? Which one will push back-
ward the other one, the smaller one or the bigger one? As
you have learnt before, what matters is the mass of the
marble: so the smaller marble that has a bigger mass will
easily shoot backward the larger marble with less mass. 4)
But you can have the glass marble push backward the
steel marble if you reduce the kinetic energy in the steel
marble. How to do this? Simply have the steel marble start
its descent from a much lower point: gravity will have a
much shorter distance to build energy into the steel mar-
ble and the glass marble will win!
INERTIA: is an effect of the
amount of Kinetic Energy
that an object has stored into
itself because of its speed
and its mass. You can clearly
see the effect of inertia if you
drop marbles down a steep
descent and then you observe how much they can go up
the following ascent. So you will notice that a steel mar-
ble will climb longer, although not faster, because it has
stored more energy in its bigger mass during the descent.
A plastic marble on the contrary will not even make it to
the top, although you would expect it to because it’s ligh-
ter, but its smaller mass didn’t accumulate enough
energy. Fascinating!
FRICTION: is another significant force that acts on mar-
bles during their run, but only to
decelerate them, even when
they go downhill. Friction is cau-
sed by the rubbing of two objects
against each other. The rougher
the materials of which they are
made, the more friction there is.
Also, the heavier the objects the more friction there is
(think of when you try to move a piece of furniture: if it is
full there is too much friction with the floor and you have
to make a big effort. If you empty it, it slides much more
easily). The surface of all objects is rough even if it seems
very smooth: just look at it through a powerful magnifying
lens or a microscope. The marbles in Skyrail Suspension
rub against the rails and produce a certain amount of fric-
tion. Keep in mind that if marbles slid instead of rolling
down the amount of friction would be much higher. To find
out which type of marble has more friction run the various
types down a gentle slope with a long flat plateau at the
end. Observe which marble goes farther: the material and
the weight of that marble generate less friction against the
rails (in fact there is no significant air resistance, so fric-
tion is the only decelerating factor, while there is not
enough speed for a noticeable inertia effect).
21