Force and Pressure

What is a force? What is pressure? How do we calculate forces and pressure?

In this post, I gonna talk about these mysterious questions. 

1. What are Forces?

A force, in everyday language, is a 'push' or a 'pull'. But would you try to push or pull open a water bottle? Of course not - you would twist it open. How else do you use forces in everyday life?

1.1 Examples

• You squeeze a tube of toothpaste.
• You stretch an elastic band.
• You twist a cap to open your water bottle.
• You fold a newspaper to make it easier to carry.

Basically, force is not only push and pull, but there are a lot of things to do with force. Just like what I said on the examples. 

2. How do we measure forces?

The S.I. unit of force is newton (N). One newton is the force that will cause a body of 1 kg to change its speed by 1 m/s, every second.

In many situations, it is important to know exactly the correct force to apply for a specific purpose. For example, in the stringing of a badminton or a tennis racket, the strings have to be stretched by the correct amount so that the rackets can perform properly without the strings breaking during the game.

A spring balance can be used to measure the amount of force applied. There are two types of spring balances - extension spring balance and compression spring balance.

2.1 Extension Spring Balance

In an extension spring balance, the spring stretches when a pulling force acts on it. the greater the force, the greater the extension of the spring. The spring is attached to a pointer, which indicates the amount of force exerted on the spring.

2.2 Compression Spring Balance

In a compression spring balance, the spring is compressed when a pushing force acts on it. The greater the force, the greater the compression of the spring. The spring is attached to a pointer, which indicates the amount of force exerted on the spring.

2.3 Formula to Calculate Forces

Formula to calculate force is:
F = Mass x Acceleration

Example:
If there is a box that has 5 kg of mass and it's being moved at constant speed of 1 m/s, the force is:
5 Newton.

3. Forces Around Us

There are several forces we encounter in our daily lives. Some common examples are gravity, friction and magnetism.

3.1 Gravity

When you throw a ball in the air, it falls towards the earth. Why? Gravitational force or gravity is the force that attracts objects to the earth.

Thus, gravitational force causes objects to fall towards the earth. Your body's weight is due to the force of gravity acting on you. In everyday use, mass and weight mean the same thing. However, in scientific use, mass and weight have different meanings.

Mass is a measure of the amount of matter in a body.

Weight is a measure of the gravitational force exerted on the object.

For example, you would weigh less on the moon because the gravitational field on the moon is weaker than the gravitational field on the earth. But your mass would remain the same since the amount of matter in you does not change.

3.2 Friction

Why is it hard to push a trolley with rusty wheels, or to pull a wooden crate over a rough floor? All these effects are caused by friction. A frictional force acts when one material rubs against another.

Friction between the ground and our feet or shes helps us walk. Without friction, we would slip or fall. Friction also helps to keep the wheels of a car on the road and stop the car when brakes are applied. Drivers are often cautioned to drive carefully during rainy weather. Why do you think this is so?

Friction can be useful, but it can also be dangerous. In factories, friction wears down machines and slow productions. Constant friction leads to wear and tear. Friction also produces heat instead of useful work.

3.3 Magnetism

Magnetic force or magnetism is the force exerted by a magnet on magnetic materials such as iron and steel.

Every magnet has a North pole and a South pole. The North pole of one magnet will repel the North pole of another magnet. Similarly, the two South poles will repel each other. We say that like poles repel each other. The force acting in this case is called the force of repulsion.,

On the other hand, unlike poles attract each other. The force acting in this case is called the force of attraction.

4. What is Pressure?

Why is it easier to pierce something with a sharp object than a blunt object? 

If you want more pressure when you pierce something with a stick, you should increase the mass of the stick but minimize the area of the stick that will have contact with something that you want to pierce.

4.1 Calculating Pressure

The formula of calculating pressure is:

Pressure = Force / Area

The S.I. unit of pressure is N/m^2 and is given the name pascal (Pa), after the French scientist, Blaise Pascal.

4.2 Pressure in Everyday Life

1. A bulldozer moves on caterpillar tracks that spread the weight of the bulldozer over a large area. This prevents the bulldozer from sinking into the soft ground.
2. The air pressure in a plane is kept at a certain level to allow passengers to breathe normally. 
3. Can openers use a large force exerted over a small area to punch a hold through a can.
4. Suction cups work by reducing the air pressure withing the cups. The higher air pressure outside the cups helps hold appliances in place.

Source: Science Matters, Volume A, Lower Secondary.

Robot Might Be Your Neighbors Soon

Are Cylons in our future? Robots can already perform complicated tasks — from navigating mountain roads to winning on quiz shows. Daniel Butler explains how science fiction is starting to look more like science fact.

Thanks to recent work in robotics, science fiction is starting to look more like science fact. Today’s robots can perform complicated tasks — from cleaning up oil spills to solving a Rubik’s Cube in record-breaking time. With advancements like that, Cylons can’t be too far off. Here’s hoping we can keep the peace.
Self-driving Audi TT
Will robots soon become our ideal chauffeurs? Considering that each year 1.2 million people die in traffic accidents worldwide, any help robots can offer would be most welcome. Luckily, car technology has been a particularly fertile sector for robotics. Move over KITT, now there’s the Audi TT. Developed by Audi and graduates from Stanford University, this car is one of the world’s most advanced robotically assisted automobiles. In 2010, the self-driving car navigated the twists and turns of Colorado’s Pikes Peak mountain. Using state of the art GPS technology that communicated its position to within less than an inch, the car finished the 12.42-mile course in 27 minutes. An expert rally driver usually reaches the 14,110-foot summit in 17 minutes.
(For more robotic cars, check out the iPad-controlled car or the Tailbot, a robotic car inspired by leaping lizards.)

Raytheon XOS 2 exoskeleton suit
Robots have been used for some time in military operations, particularly to locate and defuse bombs. Soldiers often operate these robots remotely, but the Raytheon’s XOS 2 robotic exoskeleton suit is an interesting melding of human and machine.

Like a cross between the suit that comic book hero Tony Stark dons as Iron Man and the cargo loader that Ripley maneuvers in “Aliens,” the XOS 2 enables the soldier inside to lift more than 16,000 pounds in a day without feeling fatigued. The combination of its high-powered internal combustion engine and high-pressure hydraulics makes the XOS 2 a formidable piece of kit. Although it is still being developed, this type of robot machinery may soon be seen in factories and freight yards.

Robonaut 2

The “Star Wars” film universe was heavily populated by robots, and these days they are a very real and vital part of the NASA space program. Launched on its final mission, the Discovery space shuttle carried six people and one humanoid robot named Robonaut 2. Robonaut 2 will perform routine chores and dangerous tasks onboard the International Space Station, enabling the rest of the crew to focus on their work. It can also perform maintenance and repairs on the ship’s exterior, an especially risky job for humans.
ASIMO

Designed to help people who lack full mobility, Honda’s ASIMO debuted in 2000. In 2011, a streamlined and more autonomous model was unveiled. The new model has enhanced visual and auditory sensors. These sensors enable ASIMO to process information faster and more effectively, which helps it learn from its environment. ASIMO famously appeared on the British quiz show, “QI,” in December 2011. On the show, ASIMO politely served host Stephen Fry a cup of tea, danced with contestant Jo Brand, and then beat its human competition in the quiz.
ECCEROBOT-2

This year’s stars of the Robotville Festival at the London Science Museum were two super-advanced humanoid robots, the ECCEROBOT-2 and iCub. Developed by the Artificial Intelligence Laboratoryat the University of Zurich, the ECCEROBOT-2 has realistic muscles and tendons made from elastic. This  musculature works in conjunction with 80 DC motors to mimic human movements and actions.

iCub
The iCub was created by the RobotCub Consortium, a group of European researchers who study artificial intelligence and human cognition. Standing about three feet high, the iCub has a childlike face, which uses sensors to decide which facial expressions to make.
The iCub has learned an astonishing range of tasks, including crawling, walking and archery. (It can hit the mark dead center) Its ability to mimic human actions has earned the iCub a great deal of attention — and anomination to be a torch bearer for the London 2012 Olympics.
More advanced robots will continue to rise, making a world populated by humans and humanoid robots seem less like fantasy and more like reality.

Source: http://gigaom.com

5 Coolest Home Science Experiments

5. Soda and Mentos Geyser

Watching a jet of foamy soda erupt from a bottle is not only fun, but also hysterical and will impress everyone around you… while hopefully not getting them (and yourself) too messy in the process. This also happens to be a really inexpensive home experiment, but you might want to invest in several bottles of soda and a bunch of rolls of mints just in case.

Step one: Open the 2-liter pop bottle (note: diet soda seems to work better and is less sticky come clean-up time)
Step two: Unroll the package of Mentos and prepare to dump the entire pack in at once. Fashioning a tube out of an empty toilet paper roll to just fit into the bottle mouth is very helpful.
Step three: Drop the mints in and back up a few paces… quickly!
Step four: The geyser is quite impressive and the current measured record is 21 feet!

4. Homemade Plastic

Plastics are all around us. There are many different kinds, with a wide range of properties. Some are hard, others are soft. Some are transparent, others are opaque. Most plastics are made in factories, but here’s one you can make at home!

For this experiment you will need:
1 teaspoon (5 cm3) laundry borax
1 tablespoon (15 mL) white glue (e.g., Elmer’s Glue-All)
food coloring (optional)
two cups
spoon
water

Here’s what to do:

In one of the cups, dissolve 1 teaspoon of laundry borax in 5 tablespoons (75 mL) of water. You will need to stir this for a while to get it to dissolve. (If a tiny bit does not dissolve, that is fine, though.)

In the other cup, combine 1 tablespoon of water and 1 tablespoon of white glue. If you wish, you may color the mixture with a couple drops of food coloring. With a clean spoon, stir the mixture thoroughly until it is uniform.

Put 2 teaspoons of the borax solution from the first cup into the glue mixture in the second cup. Stir the mixture.

As you stir the mixture, it will stiffen into a soft lump. After the lump has formed, take it from the cup and knead it in your hand for a couple minutes.

3. Potato Clock

Everyone can get ahold of a few potatoes, and what better way to use them (aside from consumption, that is) than to make them into an operating clock? It’s easy and only requires the use of a few things many people have handy, or, if you need to go to the electronics store to purchase an LED clock anyway, you can get the alligator clips and electrodes there, as well.

To run it on two potatoes, you’ll need:

1. Two copper electrodes. A 10-cm length of thick (0.64 cm) copper ground wire
works well. You’ll find it at hardware and home supply stores.
2. Two zinc electrodes. Use large galvanized nails, also available from a hardware or home supply store.
3. Three alligator-clip wires
4. Two potatoes.

Now make a potato clock. Open the battery compartment of the clock and remove the button battery. In the compartment, notice that there are two connections

for the battery marked plus (+) and minus (-). You’ll connect the potato battery to these two places. Let’s call the potatoes A and B. Connect A and B to the clock like this:

1. Insert a copper electrode and a zinc electrode into each potato, fairly far apart.

2. Use an alligator-clip wire to connect the copper electrode of potato A to the plus (+) connection in the clock.

3. Use an alligator-clip wire to connect the zinc electrode of potato B to the negative (-) connection in the clock.

4. Use an alligator-clip wire to connect the zinc electrode of potato A to the copper electrode of potato B.

Viola! This clock will last for months especially if the potatoes are very fresh.

2. Kitchen-Grown Avocado Tree

Avocados are delicious and highly nutritious fruits and can be used in myriad ways, but what to do with the pit? Well, you could supply yourself with even more of the green delights by growing your own tree right in your kitchen!

Step One: Open the avocado and remove the pit from the center.

Step Two: Wash the avocado pit under cool running water and towel-dry.

Step Three: Carefully push three toothpicks into the thickest width of avocado, you want to push the toothpicks into the pit about a 1/2″ deep. The toothpicks will help suspend the avocado pit in water and keep the top part of the pit in fresh air and the fat base of the pit under the surface of the water.

Step Four: Suspend the pit over a glass filled with water. The toothpicks will rest on the rim of the glass and hold the pit in place so it doesn’t sink to the bottom. Always check the water level in the glass and see that the water is covering the fat base of the pit by about an inch depth. If the water is below that level you’ll need to add some more.

Step Five: Place the glass in a bright windowsill. In about three to six weeks the top of the avocado pit will begin to split and a stem sprout will emerge from the top and roots will begin to grow at the base.

When the stem grows to about five or six inches pinch out the top set of leaves. In another two or three weeks new leaves will sprout and there will be more roots.

It’s now time to plant the young avocado tree.

1. Rainbow in a Glass

Try this at home: Have you ever seen the separate viscosities of liquids displayed like a fluid rainbow? Well, here is a simple way to take several household items and wow your friends and family alike with a beautiful use of such common materials! Remember to add each very slowly and to tint each clear liquid with some food coloring.

You will need the following materials:

1/4 cup (60 ml) dark corn syrup or honey
1/4 cup (60 ml) dishwashing liquid
1.4 cup (60 ml) water
1/4 cup (60 ml) vegetable oil
1/4 cup (60 ml) rubbing alcohol
a tall 12 ounce (350 ml) glass or clear plastic cup
two other cups for mixing
food coloring

Source: listverse.com