Abdul Wahab - science4fun

You may be listening to the word friction from your childhood that it slows down the vehicles and wear out the machine part. That is true! Friction causes resistance in motion. It is also a force that acts in opposite direction of motion.

When you put a brake on your bicycle, it stops suddenly because you increase the friction between the wheels and road. It is hard to push a box on a cemented surface than a smooth surface because cemented surface causes more friction due to its irregular surface. On the other hand, if you push the same box on a glass table, it will slide very easily because it has a very smooth surface that causes lower friction.

Types of friction

Friction has been divided into 3 types; static friction, kinetic friction, and fluid friction. All the three types of friction act on any object differently. Let’s see!

Static Friction

Static friction, as the name suggests occurs between the objects that are in contact with each other but not moving. So, that means if you place a heavy box on a table, will it experience the static friction? No!

OK so, when static friction actually occurs? Static friction will only occur between two static objects that are not moving even when the force is applied on them. For example, When you put a box on the table it won’t experience static friction until you apply a force to slide it but it still doesn’t move, then it is experiencing the static friction. But when you push the box even harder, the box will move. Now the static friction will be converted to kinetic friction.

Kinetic Friction

Now it is time learn about the kinetic friction. Let’s start with an example. Suppose you are riding a bicycle very fast. Tell me what will happen when you suddenly stop paddling? You will notice that the bicycle will start to slow down until it comes to stop completely. This is what you might guess, the kinetic friction!

If one object is moving on another object than both objects will experience kinetic friction. Kinetic friction always occurs between moving objects (In our case, the wheels of bicycles and the road). Normally kinetic friction is less than the static friction due to the motion of the objects.

Kinetic friction is further divided into two types.

Sliding friction: When two objects slide on each other, both will feel the sliding friction. Pushing a box and rubbing your hands both are the examples of sliding friction.
Rolling friction: When one object rolls on another object or both are rolling on each other, they will experience rolling friction. It is less than the Sliding friction that is why pushing a weight on wheels is easier than sliding it. The bicycle that you were riding was experiencing rolling friction.

Fluid Friction

Solids offer two kinds of friction to an object, but there is also another type of friction that is provided by the fluids, e.g. liquids and gases. Let’s see an example to understand the concept more easily.

What will happen when you drop a coin in oily liquid (your cooking oil)? It will sink slowly to the bottom. Can you tell me why? Yes, you guessed correctly. This is because of the fluid friction. The fluid (oil) is resisting the motion of the coin. Fluid friction increases with two things; one is the velocity of an object and other is viscosity (thickness of liquid) of the fluid. The honey is more viscous than the cooking, so it will provide more friction to the coin. Try it!

The importance of Friction in Everyday Life.

It helps us to walk on the road. Otherwise, we would skid away.
You warm your hand by rubbing them together.
We can stop of vehicles suddenly by putting brakes on them.
It helps you to hold a pencil or anything tightly. Without friction, the object you hold would easily slip away from your hand.

Why is Friction Avoided?

Friction cause wears in the machinery parts. So, we lubricate the machines to reduce friction
Our body joints are well lubricated to reduce friction.
Reduced fluid friction can increase the mileage of your car. After the speed of 80 km/h, we spend the majority of our fuel to fight friction.

Do you want to write some secret messages that no one can see without you? Learn how to make invisible ink from household materials, and start writing your secret messages and symbols. This is a very interesting science experiment, you will get a lot of fun.

Precaution: Always wear safety goggles and hand gloves when dealing with chemicals. Also, take the permission from your parents for the experiment, or involve them.

Method 1 – Using Lemon juice

Things You Will Need

Lemon
Cotton swap
Light bulb

How to Make

Cut a lemon into two pieces and squeeze their juice into a cup.
Add few drops of water to the lemon juice, and mix it well.
Dip a cotton swab into the mixture of water and juice. Then, start writing your secret message on a white paper.
Allow your message to dry completely.

When the paper dries, the message will disappear. When it is time to show your message just heat the paper with a light bulb by holding it over the bulb.

Method 2- Using Grape Juice and Baking Soda

Things You Will Need

Baking Soda
Cotton swap or fountain pen
Grape Juice

How to Make

Put 2 spoonfuls of baking soda into the cup.
Pour some warm water into the cup. Then, stir well.
Dip a cotton swab (or use a fountain pen) into the solution and start writing a message on a white paper.
When you finish your writing, place the paper aside and let it dry until there is no sign of your message (you can dry it in sunlight).

When you want your message to be visible, then dip any drawing brush into Grape juice and start painting it on your message.

An Electromagnet is the kind of magnet, which uses electric current to create a magnetic field. It can attract and magnetize ferromagnetic materials like Iron, Nickel, and Cobalt. It is easy to make a simple electromagnet at your home from household materials.

Things You Will Need

Thin Plastic insulated wire
5 volt AA Battery
Iron Nail

How to Make

Wrap 20 turns of insulated wire on an iron nail tightly
Trim about an inch of plastic coating from both ends of the wire.
Connect one end of the wire with the positive terminal of the battery, and other with negative terminal. Use the electric wire tape if necessary.
Get some paper clips and bring your electromagnet near them. You will see the paper clips will be attracted towards your electromagnet.

Disconnect wires from the battery, if wire or battery gets hot.

How it Works

When you connect the wires to the battery, an electric current flows in the wires. This electric current produces the magnetic field around the wire. The iron nail acts as a magnetic core. Magnetic cores are used to enhance the magnetic field.

Try It

Try to use two 1.5 volts AA batteries, and connect them in series. Then, connect the wires to this battery and observe the effects. Find out, does it affects the strength of the electromagnet
Use thicker wire instead of thin wire, and wrap around the iron nail. Then, observe the strength of an electromagnet
Use thick iron nail or bolt. Then, observe does it affect the strength of an electromagnet.

Try above methods, and note down your result. In the end, you will find which method is affecting the strength of electromagnet most.

Want to get pleasure from natural rainbow colors? But you don’t want wait for rain. By knowing science you can. In this home experiment, we are going to make a rainbow on a paper by applying the same principle that a real rainbow follows. Except that, our homemade rainbow won’t be an arc.

Things You Will Need

Small size mirror
Frying Pan (or any other similar to it)
White paper and Sunlight

How to Make

Fill the frying pan with water.
Clean the surface of the mirror and place it in the pan at an angle below the surface level of the water.
Place your pan in sunlight, such that sunlight falls on the surface of the mirror.
Hold a white paper above the pan to catch the reflected rays of the mirror.

If your setup is correct, then you should be able to watch rainbow colors on paper. If not, try to change the angle of the mirror in the pan until you see colors.

I have taken some picture on my paper and on my hand.

Watch the video of Rainbow on paper below

How to Works

When you shine sunlight on the mirror, light first enters into the water and refracts (bends). Since sunlight is a mixture of visible colors each color has its own frequency and wavelength. So, these colors refract at different angles and get separated from each other. These separated colors are reflected from the mirror on the paper.

Try it

Try using a large mirror in the water tub and note the results. Does it affect the formation of the rainbow?

A hovercraft is also called Air-Cushion-Vehicle (ACV). It uses a blower to create air currents beneath itself. Resulting in the formation of air cushion that slightly lifts the craft upward. This upward lift reduces the friction of hovercraft with the surface on which it moves. Also, the lift allows it to move freely in any direction when pushed. We will build a model of hovercraft out of home materials, and this it will use the same principle.

Things You Will Need

1 Balloon
CD or DVD Disc
Cap of a plastic bottle
Penknife
A Glue gun

How to Make

Make a small hole in the center of the plastic bottle’s cap with a penknife (Be careful).
Cover the center hole of the disc with bottle’s cap by putting it on top of the disc. Then, apply some glue to make air-tight contact. But, don’t apply glue on the hole of the cap.
Blow up the balloon and pinch its mouth.
Fit mouth of the balloon over the cap and release it.

Your hovercraft is ready and working. Put it on a smooth surface, and push it in any direction you want. It will go there smoothly.

How it works

Air from the balloon passes through a hole in the cap. Then, it flows beneath the disc creating an air cushion that slightly lifts the disc up. As a result, the friction between surface and disc reduces. This reduced friction allows the hovercraft to move freely in any direction where it is pushed.

Try It

Use large size balloon, instead of small size balloon.
Make two more holes in the disc and cover each hole with a cap. Then, blow three balloons and fit them to the caps (This is easy with three people each handling one balloon).
Try to land your hovercraft on water and sand.
Check out! How much weight your hovercraft can lift. Try with paper clips, pencils, and rubbers.
Think! What can you do to increase the payload capacity of your hovercraft?