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It's All in the Way You Move

© Linda Bond

Motion is a part of physics which studies how things move. Most things can't move on their own, so movement usually occurs when one or more forces act on the object being observed.

Once something starts moving, we can measure how fast it is moving, or its speed, and assign a common term to describe it's speed in relation to other objects. This might be miles per hour (mph) as in the case of an automobile or meters per second (m/s) which is the unit of measurement most often seen in physics. Because movement may speed up or slow down, it is often handy to describe the average speed of the moving object. We can do this by dividing the total distance traveled by the total amount of time it takes to move from beginning to end. The resulting figure is the average. For instance:

5 miles distance divided by 5 minutes = 1 mile per minute or 1 mile every 60 seconds

3 feet distance divided by 10 hours = .3 foot every hour or 3.6 inches per hour

I don't know. A snail maybe?

Sometimes we want to know the direction in which an object is traveling as well as the speed at which it is moving. As weird as it may sound, velocity can change even when the speed of an object stays the same. That's because a change in direction causes a change in velocity. If you go round and round in circles, for instance, your velocity will change all the time because your direction is changing.

If I drive my car toward Canada from the U.S., at let's say 50 m.p.h., I can say that my velocity is 50 miles/hour north. If I whiz past you standing on the side of the road, you will sense that I am moving at about 50 mph. If, on the other hand, you drive your car next to mine, at the same speed, my velocity will appear to be zero in relation to your car. This is called relative velocity.

Now, if I step on the gas, my speed will accelerate. Again, in physics it would be measured at meters per second per second. What? This means that for each second, I will be moving one meter per second faster. After two seconds, I will be moving two meters per second faster than I was originally, and after three seconds, I will be moving three meters per second faster. Oh.

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