Teaching Physics in the Primary Grades

Even today, Newton's laws of motion are the basis of understanding the movement of objects in the world around us. Through the use of toys and clear explanations, your elementary school students can understand the basics of Newtonian physics





1. Put a small toy  animal or doll on top of a skateboard. Give the skateboard a shove. When the board starts moving, the animal will slide back. When the board hits the wall and stops, the animal will slide forward.

2. Use the skateboard to explain the concept of inertia, the first law of motion. The toy on top resisted moving at first when it slid back. Once it was moving, it resisted stopping by sliding forward. So things at rest tend to remain at rest, and things in motion tend to remain in motion.

3. Set up a wall made out of wooden bricks in the center of the room with a ramp in front of it. Run a small toy car or marble down the ramp and have the students observe it not knocking over the bricks. Then run a larger, heavier toy car or marble down the wall and watch it knock over the bricks.

4. Explain that force equals mass times acceleration. The second car had more mass, so it had more force.

5. Set up the wall again. This time, start the heavy car from low down the wall and watch it not knock over the bricks. Then, start it higher up and have students observe it knock over the bricks.

6. Explain that the car had more acceleration when it started higher on the ramp, which caused it to knock over the bricks.

7. Use a Newton's cradle to teach  the third law of motion: For every action, there is an equal and opposite reaction. Explain that when the first ball hits the second ball, the second ball reacts by hitting the third ball, and so forth, sending the last ball flying. Use marbles, Hot Wheels cars and other toys to demonstrate this principle again.

8. Have students use marbles, Hot Wheels cars and other toys to demonstrate the third law of thermal dynamics. If nothing else, they will appreciate the chance to crash cars into each other.


Classical Physics


Classical physics was the basis for all understanding of how the universe worked for hundreds of years before Albert Einstein and the era of modern of physics arrived. Classical physics was developed in 17th century England by Sir Issac Newton and revolutionized how people saw the world. Three of the basic rules of classical physics are the laws of motion which define the relationship between the motion of an object and any forces acting on it. It's important to use practical examples when teaching  these laws to children.


Newton's First Law

Newton's first law says that if an object is either at rest or moving, then without outside forces acting on it the object does not change its motion. Think about a car  at rest. It won't move until it's started up and the driver pushes the gas pedal. Then, if the car is sped up to a speed and put on cruise control, it won't change again until the driver accelerates or hits the brakes. If a car has infinite gas and no forces (like gravity and acceleration) act on it, the car will drive on forever. 

Newton's Second Law

Newton's second law says that how fast an object is sped up (its acceleration) due to a force, multiplied by the mass of the object, is equal to the amount of force pushing on the object. This law is saying that if you push two objects with different weights with the same amount of force then the lighter object will speed up faster than the heavier one. Think of punching a balloon compared to punching a bus.

Newton's Third Law

Newton's third law says that for every action, there is an equal and opposite reaction. This means that for every push on an object there is an equal push in the opposite direction. Think about standing on the ground. The weight of your body is pressing down on the ground and unless something wasn't pushing back up at you, you would fall right through the Earth. This is the third law in action. The Earth pushes back at you with exactly the same push that you exert against the Earth.


These laws are used for all kinds of calculations in physics, engineering and other sciences. The laws help scientists  predict the motion of objects with one or more forces acting on them. Because force, mass and acceleration are so closely related, if a scientist doesn't know one, he can calculate it if he knows the other two. Some forces that act on you everyday and affect how fast you move include friction, gravity and the normal force, which is the force that pushes up at you from the ground.

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