Science Project Ideas for Kids

There are two types of mechanical waves: transverse and longitudinal. A type of mechanical wave energy that causes the medium (material) through which is travels to be disturbed. The movement of the medium is in a direction that is perpendicular (at right angle) to the direction of the wave. In other words, if the energy is moving horizontally, the medium is displaced in an up and down direction.

Transverse Wave: A mechanical wave is a type of energy that disturbs the medium through which it travels. This means that the energy requires a material in order for the energy to be transmitted from one place to another.

In the photo a lady has jumped onto a trampoline causing the surface of the trampoline to be pushed down in the area where she landed. In other words, the surface of the trampoline was disturbed and the the amplitude of this disturbance is equal to how far down the surface was pressed. The results is a connecting spot, under where the man was sitting  on the trampoline suddenly rises with enough energy to throw the man up into the air as shown. The stretched surface under the lady’s feet will spring back into its original shape with enough energy to throw the lady upward for a short distance. If the man falls so that he hits the trampoline at the right time he will push the surface down which will add to the energy throwing the lady upward.

Longitudinal Wave: A type of mechanical wave energy that causes the medium through which it travels to be disturbed. The movement of the medium is in the same direction as is the direction of energy.

In the diagram, a slinky is used to demonstrate a longitudinal wave. The energy is moving to the left as will be the displacement of the coils. As shown the coil is laying horizontally with some of the coils squeezed together at the right end.

Assuming that the ends of the slinky are secured, when the compressed coils are released, they will spread out pushing the coils in front of them together–compressing them. Shown in the second diagram of the slinky.

In the bottom diagram, the parts of a longitudinal wave are identified and defined. Since the slinky is secured at each end the wave energy bounces back and forth from one end to the other.

Physics For Every Kids

The best way to learn is from experience, and the more of your senses that are stimulated the longer  lasting is the memory.

I have a memory of doing an exercise with a strong elastic rubber rope with loops on each end. The rope had a larger diameter than the one shown in the picture, but it was used in a similar way. Note that one end of the rope in the pic is secured to a closed door. It’s not very clear, but it looks like it is attached to some lock. The person is pulling on the rope–stretching it. When stretched the rope has elastic potential energy. If the arm became relaxed so that it no longer applied a force to the rope, the stretched rope would quickly return to its natural (unstretched) shape. In fact, if the elastic potential energy is great enough, relaxing the arm could result in the person being pulled toward and being slammed into the door. No! This was not my experience.

See if you can picture me doing this exercise.

1. Loop one end of the rope over a door knob (Round door knobs were the style.)
2. Sit on the floor near the door and place the free rope loop over one of your feet.
3. Lay down so that your leg is comfortably raised with the rope at full length but not stretched.
4. Raise your leg as far as possible. The objective is to stretch the rope as much as possible, and then slowly lower your leg. Repeat 5 times.

Science Application: Stretched Rope has elastic potential energy.

Now Make a Mental Picture of this:

I was partially sitting and raised my leg as instructed. Without warning the door knob was pulled out of the door and propelled forward. Due to the pull of gravity, my forehead was directly in the pathway of this projectile. It was truly a moment in which I saw stars twinkling. I can confirm that even after forty years the experience is as clear as when it happened. I can also confirm that the stored elastic energy of the rubber rope was transferred to kinetic energy and that a moving object really hurts when it hits you in the head. I decided that this exercise was not good for my health.

A mechanical wave is a type of energy that disturbs the medium through which it travels. This means that something physically moves.

Transverse Wave: A type of mechanical wave energy that causes the medium (material) through which is travels to be disturbed. The movement of the medium is in a direction that is perpendicular (at right angle) to the direction of the wave. In other words, if the energy is moving horizontally, the medium is displaced in an up and down direction.

In the diagram, the direction of the medium’s displacement is up and down, and the movement of the energy is horizontal and to the right. Water waves are a typical example of transverse waves, but the energy that moves through the rubbery material of a trampoline provides a more visual model of how the molecules of the medium are displaced. Click   HERE for details. OOPS! I DIDN’T FINISH THE SECOND HALF OF THIS —SO I’LL FIX IT AND HAVE A BETTER POST FOR YOU TOMORROW.

Janice

Question: How fast can the Jesus Lizard run on water?

Answer:

The lizard is called a  “Jesus Lizard” because it can run across the top of water. This is because the lizard has large hind feet with scaly fringes on the sides of the third, fourth, and fifth toes. As you can see in the photo, these fringes are pressed  the toes when this lizard walks on land.

Living near water, when the lizard senses danger it heads for water, spreads the fringes and off it runs at a speed of about 5 feet (1.5 m) per second across the water’s surface.

The spread fringes increases the surface area of its feet and as it quickly slaps it feet against the water’s surface, a tiny bit of air is trapped between it feet and the water. This ever so tiny air pocket acts much like itsy-bitsy flotation devices. Even so, the lizard can only run so far, about 15 feet (4.5 m) before gravity wins and the lizard sinks.

No problem, the lizard is an excellent swimmer and can stay underwater for long periods of time.

DID YOU KNOW?

Location: Tropical rain forests of Central America, from southern Mexico to Panama

Size: 2 to 2.5 feet (61 to 76 cm) including tail

Weight: up to 7 ounces (200 g)

Miscellanies Adaptations: Can run on water, excellent swimmer and capable of staying under water for up to 30 minutes.

Science For Every Kid: Geography