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Fu-Kwun Hwang
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 « Embed this message on: February 20, 2013, 10:48:15 pm » posted from:,,Satellite Provider

In  your science class, you will learn about Newton’s laws of motion. Do you know why these laws are so important? When you throw a baseball or you bounce a basketball on the court, you can use Newton’s laws to explain the motion of the baseball or basketball. In fact, almost all motion in the world can be explained by these laws. Newton’s laws are useful when people design airplanes, trains, cars, sports equipment, toys, and many things that have to do with motion. Some people have trouble understanding Newton’s laws of motion because it’s hard to see
how the laws work without any examples. One great way to understand  these laws is to look at how they relate to cars in everyday life.

The First Law of Motion

“Every  object persists in its state of rest or uniform motion in a straight  line unless it is compelled to change that state by forces impressed  upon it.”

Can  you see why it’s hard for some people to understand the first law?  Those are some complicated words. To help you to understand better,  let’s break it down and use the example of a car. The first part deals  with an object in a “state of rest”. This means that the object is not  moving. When your mom or dad parks the car in the garage or the shopping  mall, the car is said to be in a “state of rest” because it is not  moving. The car will not move until the engine is started and somebody  drives it away. The second part deals with an object in “uniform  motion”. This means that the object is moving at the same speed. When  you mom or dad is using “cruise control” on a highway at 60 miles per  hour, the car will be moving at that speed in a “straight line” until  something happens to change it. What is this change? It depends. By  using the brakes, your mom or dad can slow the car down or bring it to a  stop. On the other hand, the car’s direction will be changed if it is  hit by another motor vehicle.

The Second Law of Motion

“Force  is equal to the change in momentum (mV) per change in time. For a  constant mass, force equals mass times acceleration.” F = ma

This  is one of the most important formulas in physics. Again, some people  may find it hard to understand this law because of the use of some big  words. However, the idea is very simple because you may already know how  it works in real life. Do you need more energy (force) to move a book  or a large screen TV? Surely, you know that you need more energy to move  a large screen TV, right? That’s what the second law of motion means.  Using our example of cars, you should know that it takes more force to  move an 18 wheeler truck than a car. This is why the engine in an 18  wheeler is more powerful than the engine in a car. To move a heavier  object, you need to use more force.

The Third Law of Motion

“For every action, there is an equal and opposite re-action.”

Finally,  here’s a law without any complicated words. As you will see, it’s quite  easy to understand Newton’s third law of motion. Do you like to go  skating? The next time you go for a skating trip, try to this simple  experiment. With your skates on, find someone and place your palms  against the other person’s palms. Then, push off and you will see the  both of you going in opposite directions. Do you know how cars move?  Now, you may think that a car moves because of the engine. Well, the  engine is the source of power but it’s not what makes a car move forward  or backward. When you press on the accelerator, the wheels spin and the  force of the tires push off against the road, causing the car to move.  This is Newton’s third law of motion in action.