Pages from 55 experiments from nature

TOMISLAV SENĆANSKI

Read interesting stories about plants and animals.

Discover the physical phenomena occurring in the living world.

Find places where you can explore the nature.

Meet the scientists who have studied the physical phenomena.

Find out if the plants and animals know physics!

DO PLANT ALS M I N A D N A S! C I S Y H P KNOW

55 EXPERIMENTS FROM NATURE

Perform experiments and probe the physical phenomena of nature.

55 Illustrated by

Jovan Ukropina Nikola Vitković

TOMISLAV SENĆANSKI

FROM NATURE

55 IF FIND OUT ND PLANTS A W KNO ANIMALS PHYSICS!

Tomislav Senćanski

from Nature Illustrations

Jovan Ukropina Nikola Vitković

W

henever you get the opportunity, explore nature.

Scientists, too, explore it and make experiments, thus getting to know our precious environment.

Nature awaits you. It has many interesting adventures in store for you. Occurrences which accompany the living world are based on numerous laws of physics, they just need to be discovered and studied with pleasure.

If you wonder where all that interesting stuff is, this book will help you find the answer. It contains some stories from nature and the presented physical occurrences which are related to them.

See for yourself that exploring is nice and exciting and that nature is a great school.

How TO

This Book

use

1.

1. Story from Nature represents a description of a plant or an animal species and a representation of its characteristic induced by a physical occurrence.

2. How Is This Possible?! is an actual explanation of a physical occurrence from the living world.

3. Learn more is the label which leads you to more stories from nature.

They are a part of the chapter “Places Where You Can Explore Nature�.

Read the one which is on the corresponding page.

4. See for Yourself represents the chapter with an experiment you can perform. Along with this title, the examined physical phenomenon is specified.

5. Things You Need is a list of things you need to collect in order to perform an experiment.

6. Experiment is the description of the work process. Start from the first picture and follow instructions step by step.

7. What Happened? illustrates what happened at the end of the experiment.

8. Reason is the title of the text in which the studied physical occurrence is explained in more detail.

9. The Experiment Plus tag leads you to the page with extra assignments.

Under the corresponding number, you will find assignments related to the subject you are studying.

10. The text next to the portrait of a scientist tells about the scientist who explored that field.

11. Interesting Thing is a text related to the examined physical occurrence.

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Manual

for Conducting Experiments

Before

You Begin‌

1. 1. Plan precisely what you are about to do in the experiment.

2. 2. Collect everything you need for the experiment.

3. 3. Think through whether or not you need help in conducting the experiment.

4. 4. Find a suitable spot where you can perform the experiment.

5. 5. Make sure you have ample time to work.

6. 6. Let no one distract you while you are working!

Planning an experiment is very important. However, even with a good plan, mistakes can happen. That is normal. Every explorer makes mistakes sometimes. If that happens, think carefully, and then repeat the experiment.

Everything will probably go well then.

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Once

You Get Started‌

1. Take into consideration that some experiments require plenty of time and patience.

2. Use the devices which can hurt you (saw, knife, scissors, matches, and the like) in the presence of an adult.

3. Be careful not to damage anything while making an experiment.

4. Do not forget to write the measured values into a notebook during the experiment!

If a result surprises you, repeat the measuring. That is how you will make sure that everything has been done properly.

5. Take photographs of the phases of the experiment which you think could be useful later.

6. After the experiment, do your best to clean the space in which you have work

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Futile Chase

M

any tales have been told about the sly, clever and daring fox. Its cunning is the theme of numerous fables.

In the woods it inhabits, the fox mainly preys on mice and rabbits. Its reddish fur blends into the surroundings so well that the fox can hardly be noticed while slowly approaching its prey. When there is not enough food in the woods, the fox goes to villages and catches poultry. That is why farmyards are guarded by dogs, and hunters organize chases which are highly dangerous to foxes. But, although foxhounds run as fast as the fox, the fox still very often manages to get away.

How

is This Possible?!

10

While fleeing, the fox constantly changes the direction of movement, during which it keeps its balance by moving its big and strong tail left and right. Sometimes it suddenly turns over on one side, and then leaps quickly and runs in another direction.

Foxhounds cannot keep up with the fox’s constant deflection, and once the fox reaches the woods and the den, it is safe.

When the fox changes the direction of movement, the foxhound chasing it is in full speed and cannot stop right away. The characteristic of a body to continue moving in the same direction is called inertia.

For that reason, the foxhound keeps moving forward for a while before it turns and continues to chase the fox.

Thingrss you Need:

See for Yourself ••• Body Inertia

• traine • running track

1. Runner at the finish Determine the running track at least 50 m long.

Mark the trail at the start and the finish.

Start running fast from the start to the finish line.

What

Happened?

Reason

When you reach the finish line, stop as quickly as you can and mark the spot where you stopped.

You will see that you will not stop right at the finish line, but you will move forward for a while, gradually slowing down.

It happens because your body tends to keep moving.

Experiment Plus

(26 and 27) >> 11

Jet Propulsion

T

he cuttlefish is a sea animal. It belongs to the group of cephalopods – mollusks with arms on the head which they use to catch prey. The anatomy of the cuttlefish is the most complex among the invertebrates. Its back side is covered with a mantle whose edges, like a fin, enable the cuttlefish to swim. In the inside of its body, there is a porous, but solid structure made of calcium carbonate – cuttlebone. Thanks to it, the cuttlefish can float in water.

The cuttlefish is very mobile and is an excellent swimmer. This is made possible by a funnel-shaped organ on the side of its body. The water from the cavity under the mantel is in forceful jets ejected from the body through the funnel. The cuttlefish thus moves in the opposite direction, that is, forward. It can change the direction of movement by altering the position of the funnel.

How

Is This Possible?!

12

When the cuttlefish forces a jet of water through the funnel, it exerts action force on the water. Simultaneously, the water exerts reaction force on the jet, thereby affecting the cuttlefish as well. The force’s direction is opposite of the one of the jet and it pushes the cuttlefish forward.

Things You Neede :of wooden board

See for Yourself ••• Action and Reaction Forces 2. Rocket Launch Make a model rocket from the wooden board.

Carve a small canal on the upper side of the board; the canal must reach the rear end of the rocket.

Slowly put the model rocket on the surface of water and pour a few drops of oil into the canal.

Observe what happens when the oil leaks into the water.

What

Experiment Plus

Happened?

Reason

• a piec • a wood saw • a wood file bucket • a large bowl or a of water • oil

When the oil starts to pour from the rear end into the water, the rocket is moved forward.

(28, 29 and 30) >>

The pouring oil has the backward direction of action in relation to the body of the rocket, which is the action force. The rocket then moves forward due to the agency of the reaction force.

Isaac Newton (1643-1727)

was an English physicist, mathematician and astronomer. Newton established the Law of Universal Gravitation, to which all bodies in the universe are subjected. He also established principles of mechanics which form the basis upon which the force and the interaction of bodies are defined.

Do Not Forget!

The action and reaction forces appear simultaneously!

13

The Gymnast Pine

P

lants are sensitive to the stimuli they receive from their environment and respond to them by bending in the process of growth.

Light is an important developmental factor. While growing, a plant directs itself towards the source of light, trying to position every leaf so that they could be lit by sunbeams most efficiently. Some plants look like mosaics made of leaves, because the leaf stems elongate and curl as they grow in order not to occlude other leaves.

A pine in a forest grows straight upwards, so that it exposes pine needles to the sun as much as possible. However, if we observe a pine on a sunny slope, we will see that it stands straight even when there is enough light and no other plants to block the sun. This means that light is not the only stimulus which affects it. The pine grows upwards under the influence of the gravity of Earth.

There are parts of plants which respond to the light stimulus in such a manner that they grow away from light. That is the case, for example, with aerial roots of the ivy by which the plant anchors itself to the soil.

How

Is This Possible?!

14

One of the most important stimuli which affect plants is Earth’s gravity.

It is the force with which Earth attracts to the center every object and everything in its environment. The parts of a plant above the soil grow upwards (in the direction opposite of the force of Earth’s gravity). The pine on the steep slope bends during growth until it reaches the position in which Earth’s gravity exerts force.

>>Learn more about Earth’s gravity, p. 80

Things You Needse: eds which have

See for Yourself ••• Earth’s Gravity 3. Growth under Earth’s Gravity After a week, carefully remove Sow a few seeds in the flowerpot.

Water the sprouts every day.

the plants from the earth and wrap them in pieces of cloth.

Insert one plant into each bottle containing a small amount of water in such a way that a piece of cloth closes the opening. Put the bottles into horizontal position and place them in the box.

Observe the growth of the plants on the next day.

What

Happened?

The part of the plant in the bottle started to bend downwards, and the part outside the bottle began to grow upwards.

•• bean r germinated in wate rth •• flowerpot with ea •• a piece of cloth les •• small plastic bott •• water t should Note: The experimen ht lig be performed in dim be ld ou and the plants sh e stored in a dark plac ve u ha immediately after yo board rd ca A . dealt with them rve as se box with a lid could a dark storage.

Experiment Plus

(31 and 32) >>

The plants were influenced by Earth’s gravity. The characteristic of a Reason root is to grow in the direction of the exerted gravitational force of Earth, whereas a trunk and leaves grow in the opposite direction.

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