Acceleration

is when the speed at which an object is traveling is further increased. The object travels faster because some force is applied to push or pull the object, making it move more quickly. In physics, when calculations are made concerning acceleration, it is usually represented by the symbol α and is measured in metres per second, per second or metres per second squared (written in mathematical shorthand as ms^-2).

When bodies fall freely under the influence of the force of GRAVITY they all fall at the same rate, that is at a uniform acceleration. Whether the object is a lead weight or a feather they fall at the same rate due to gravity. The reason that in reality the lead weight hits the ground before the feather is due to air resistance holding back the feather. Acceleration due to gravity is approximately 9.8 metres per second per second so when the air resistance is very little, the velocity (speed) of a falling object increases by 9.8 metres per second, per second. On the other hand, an object shot straight upwards with a particular velocity will slow down (decelerate) by the same rate every second until it reaches its greatest height after a particular period of time. When this maximum height is reached, the object that had been shot straight upwards (no horizontal motion whatsoever) will start to fall with an acceleration of 9.8 ms-2.

Taken from Dictionary of Science

_____________________________________________________________

In physics, and more specifically kinematics, acceleration is the change in velocity over time. Because velocity is a vector, it can change in two ways: a change in magnitude and/or a change in direction. In one dimension, i.e. a line, acceleration is the rate at which something speeds up or slows down. However, as a vector quantity, acceleration is also the rate at which direction changes. Acceleration has the dimensions L T⁻². In SI units, acceleration is measured in metres per second squared (m/s²).

In common speech, the term acceleration commonly is used for an increase in speed (the magnitude of velocity); a decrease in speed is called deceleration. In physics, a change in the direction of velocity also is an acceleration: for rotary motion, the change in direction of velocity results in centripetal (toward the center) acceleration; where as the rate of change of speed is a tangential acceleration.

In classical mechanics, for a body with constant mass, the acceleration of the body is proportional to the resultant (total) force acting on it (Newton's second law):

where F is the resultant force acting on the body, m is the mass of the body, and a is its acceleration.

Taken from Wikipedia

FACTS ABOUT YOUR BODY

HOW FAST DOES AIR TRAVEL WHEN YOU SNEEZE?

A hundred miles per hour.


WHAT MAKES YOUR KNUCKLES CRACK?

Bubbles popping! There is fluid around the joints of your finger bones. When you stretch your fingers, the pressure on the fluid changes, little bubbles form in the fluid and they pop. Want to crack the same knuckles again? You have to wait about 15 minutes.


HOW DO YOU GET "GOOSE BUMPS"?

Each hair on your body grows in its own shaft, called a follicle. If you get cold or scared, the smooth muscles around the follicles contract. This gives you goose bumps and makes the hairs stand upright.


HOW LONG DOES AN EYELASH LIVE?

About 150 days.


WHY DO SOME PEOPLE HAVE DIMPLES?

Dimples are caused by muscles on your face. These muscles are unusual because they are attached to the skin; most muscles are attached to bones. When people smile, certain muscles make dimples.


WHAT IS THE LARGEST BONE IN THE BODY?

The largest bone in the body is the thigh bone.


WHEN ARE PEOPLE THE HEALTHIEST?

People are the healthiest between the ages of five and 15.


WHEN DO KIDS STOP GROWING?

Boys achieve 98% of their height when they reach the age of 17 and three-fourths. Girls reach 98% of their height when they are 16 and a half.


HOW LONG DOES IT TAKE TO BLINK YOUR EYES?

About three-fourths of a second.


WHAT IS THE HEAVIEST ORGAN IN THE BODY?

The liver. It weighs three and a half pounds in an adult, or about five times more than the heart.


WHEN IS YOUR EYE STILL?

Never! The eye is always moving, even when you are staring at something. The tiny muscles in the eye move about 100,000 times a day to let you see. For your leg muscles to get the same exercise, you would have to walk 50 miles.


HOW MANY SOUNDS CAN YOU HEAR?

You can hear between 350,000 and 400,000 different sounds.


HOW MUCH AIR DO THE LUNGS USE IN ONE DAY?

About 12,500 quarts.


WHY DO PEOPLE YAWN?

In the lungs are millions of tiny air sacs called alveoli. Changes in the alveoli cause you to yawn. When you are sleepy, you are not breathing deeply enough oxygen. The alveoli are not filled with air. So your brain sends out a message telling you to take a long breath. That long breath is a yawn.


WHAT IS THE HARDEST SUBSTANCE IN THE BODY?

If you guessed that it is the bones, you are wrong. The hardest substance is the enamel that covers your teeth. However, like other parts of the body, the enamel cannot fix itself when it is damaged.


HOW MANY DIFFERENT SMELLS CAN HUMANS SMELL?

The average person knows 4,000 different smells. Some people with a very special sense of smell know 10,000 different scents. People who test perfumes have this talent.


HOW MANY MUSCLES DOES IT TAKE TO SMILE?

It takes 17 muscles to smile. Forty-three muscles are used when you frown.


HOW IMPORTANT IS THE THUMB?

The thumb does 45% of all the work done by your hand.

Condensed from Macmillan Illustrated Almanac for Kids

The Wagon Train Out of Jail

If you had the choice of traveling around the United States by a wagon train, sailing on a 130-foot schooner, camping in the wilderness or serving time in a detention center, which would you choose?

As unusual as this may sound, some offending American teenagers are given this choice.

Authorities who work with young offenders say many young people involved in vandalism, stealing, shoplifting and similar offenses have often just made bad decisions without thinking about how their actions affect others.

With this is mind, alternatives to juvenile detention have become popular among some law enforcement officials.

Some teens in trouble now have alternatives to jail terms.

One example is VisionQuest. Those involved must make a one-year commitment, abstain from involvement with sex, drugs, alcohol and tobacco during their stay and complete three VisionQuest programs, some of which are listed below.

Quests. Quests may be cross-country horseback or bicycle expeditions or a several week guided trek through forest land.

Wagon Trains. Participants travel across the United States with a group of 10 to 12 mule-drawn wagons.

OceanQuest. Young people learn navigation, water safety and sailing techniques aboard one of two schooners.

Through these programs teens develop positive relationships with others. The many lessons they learn include cooperation, self-discipline, teamwork, respect for authority, responsibility and the work ethic.

Each of these programs includes four hours of school classes a day, five days a week.

Similar programs are growing in popularity. Some authorities believe teens can turn their lives around better through counseling and working with others than by sitting in a jail cell.

-By Larry Johnson

Taken from Youth 90 magazine