This week lesson is very interesting, we will learn about Motion

Chapter 15 Force and Motion

Lesson 1: What Is Motion?

VOCABULARY

Motion

Distance

Speed

Types of Motion

Suppose you are on the playground. What kinds of motion do you see? A girl throws a ball forward. It curves up and then falls down. A boy bounces a basketball. It goes up and down. Some children run fast and zigzag as they play tag. Others go back and forth on swings or up and down on seesaws. Still others go round and round on a merry-go-round.

You can observe many kinds of motion on a playground. The next time you are on a playground, think about all the ways you move.

An object can keep traveling in one direction, or it can change direction. Objects can move fast or slowly.

Every object has a position or location. A school bus stops at the same position every day, so you know where to wait for it. You know the position of the cafeteria in your school. The cafeteria’s position does not change. What is your position right now?

Motion is a change of position. To get to the cafeteria, you would need to change your position. You would need to move. When you ride a bike down the street, the bike changes position. It is in motion. If you park the bike in a bike rack, the bike is no longer changing position. It is no longer in motion.

COMPARE AND CONTRAST What is one way in which each kind of motion is different from the others? How are all kinds of motion the same? Distance, Direction, and Time Suppose you are on a trip with your family. You ask, "How far do we have to drive to get to the next city?" What you want to know is the distance. Distance is how far it is from one location to another. Distance is often measured in inches, yards, or miles. Scientists use units of centimeters, meters, and kilometers. You can use a ruler to measure distances. An important thing to know about motion is its direction. Your family’s car is going east from Chicago to New York. Your friend throws a ball up into the air.

The greyhound is a fast runner. It can cover a long distance in a short time.

This ice skater is going very fast and travels a long distance in a short time. Her direction changes as she rounds the curves of the track.

Another important thing to know about motion is time. Time is a measure of how long it takes for an object to move. Something that moves fast covers a long distance in a short time. A fast third-grader can run a 50-meter dash in 10 seconds. A snail needs an hour to crawl the same distance!

In science, time is often measured in seconds. Other units of time include minutes, hours, days, and years.

COMPARE AND CONTRAST You are walking home from school. Your parent is driving from your home to school. How is your motion different from your parent’s? The motion of this honey is slow. Its direction is straight down Speed Speed is the distance an object moves in a certain period of time. Suppose a lion could run 80 kilometers (50 miles) in one hour. You find its speed using both distance and time. Suppose that things travel the same distance in different amounts of time. They would have different speeds. A third-grader who runs the 50-meter dash has a speed greater than a snail that travels 50 meters. What if two objects traveled for the same amount of time but they went different distances? The object that traveled farther had a greater speed. COMPARE AND CONTRAST Suppose a zebra runs 15 kilometers in one hour. A grizzly bear runs 10 kilometers in one hour. Which animal has the greater speed?