real science for today's homeschooler

Earthquake Waves

Earthquake Waves

The general properties of waves can be investigated through an activity on earthquakes. First, have your child research the three different types of earthquake waves. Encourage them to find the following information about each wave:

1. name of the wave

2. how quickly it travels compared to the other two

3. what part of the Earth does it travel through

4. type of wave, based on motion (compression wave, transverse wave, etc.)

5. does it cause damage to buildings

Help your child organize the information they find into a chart or data table. This can be done on the computer or by hand. Or, make a poster and add pictures and drawings. Use the chart to compare and contrast the three types of earthquake waves.

Next, have your child build a structure that will withstand the different types of earthquake waves. (Encourage them to look at the type of motion caused by each wave.) Use any type of materials such as building blocks, boxes, DVD cases, etc. In order to test their construction, have them build it on a surface that will be easy to move, such as a small table, board, etc.

Test the structure(s) by recreating the various motions of the different earthquake waves:

P waves – move the surface back and forth in a horizontal motion

S waves – move the surface up and down

L waves – move the surface in all different directions, including circular motion

Older children may then want to research how scientists are designing earthquake resistant buildings.

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Rotational Motion with a Pinwheel

Rotational Motion with a Pinwheel

Kids love to play with pinwheels. Whether you buy one at the store or make your own (pinwheel making tutorial), add a little Physics to the fun!

1. Use a string and ruler to measure the outside distance around the outside of the pinwheel.

2. Mark one spot on the pinwheel in some way. Use color, a piece of tape, etc. Just make sure the mark is very visible, even when the pinwheel is spinning.

3. Have your child practice watching the pinwheel in motion and counting each time the pinwheel makes a complete revolution. (When the mark on the pinwheel goes all the way around and returns to the same spot.) Move on to practicing counting exactly 10 revolutions. When your child has this down, move on to step 4.

4. Use a stop watch to measure the time it takes for the pinwheel to make 10 revolutions. Repeat 5 times, then average the 5 trials to get the “average time” for 10 revolutions.

5. Divide the average time by 10 to get the time for 1 revolution.

6. Calculate the speed at which the outside of the pinwheel was spinning by dividing the distance around the outside of the pinwheel (step 1) by the average time for 1 revolution (step 5). Your child has just calculated the rotational speed of the pinwheel!

To extend, repeat using different sources of “wind” to move the pinwheel at different speeds. Add a weather component by repeating on consecutive days to compare the wind strength. Older children may find it interesting to compare the actual wind speed (use a local weather app) to the speed of the pinwheel rotation. Look for patterns and mathematical relationships between the two.

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How do colors affect temperature absorption?

How do colors affect temperature absorption?

We’ve all heard the fashion sayings . . . “never wear white after Labor Day” . . . “pastel colors should be worn at Easter” . . . etc. You know the traditions, but did you know they are actually based on science? The color of the clothing you wear can affect how hot or cold you feel when standing outside during the day.

The light reaching us from the Sun is known as “white light” and it is really made up of all the colors of the rainbow. Each of those light rays coming in contains energy. White materials reflect all colors away from their surface, absorbing none of the light energy. Similarly, light pastel colors reflect almost all the incoming light energy. Black materials absorb all light rays, allowing none to be reflected into our eyes. (That’s why it looks “black.”) Dark colors absorb almost all the incoming light energy.

So, you wear light colors in spring and summer to stay cool, and dark colors in the winter to stay warm. Fashion traditions are based on science! You can investigate this phenomenon with your children to prove that it works:

1. Select two t-shirts. Ideally, use one black and one white. If you don’t have black and white, use one that is as dark as possible, and one as light as possible. Also, select t-shirts that are similar in size and fabric type.

2. If possible, do the experiment outside on a warm, sunny day. Select a spot where you can lay the t-shirts out flat, side-by-side. Try not to set them on metal as this will affect the temperature.

3. If you have two similar thermometers, you can just insert a thermometer inside each t-shirt, wait for a select amount of time, and then read the thermometers. Try waiting about 15 minutes and then check for a temperature difference. Increase the time if necessary. Time will depend on the intensity of the sun that day.

4. If you only have one thermometer, try putting some water in two plastic baggies. Be sure to use the same type and size baggie, and the same amount of water. Place one of the baggies of water into each t-shirt at about the same place. Increase the time to about 30 minutes since it will take longer for the water temperature of the water to change noticeably. Be sure to check the temperature of the water in place. Bringing the water into the cool house can drop the temperature significantly while waiting to check the second bag.

To extend the experiment, especially for older children, repeat with different “medium” colors or prints to see what effect each has on temperature. You might also want to test how different types of fabric affect the absorption of light energy. Your children can then write their own “fashion rules” based on science!

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Learning about Buoyancy in the Pool

Learning about Buoyancy in the Pool

Buoyancy seems like a simple concept, but to fully understand it on a scientific level can be a challenge for students. Introduce the concept to your younger elementary kids in a fun way while playing in the pool this summer!

Buoyancy is based on Archimedes’ Principle that states, “Any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object.” Very confusing language for kids! Here’s how to explain Archimedes in their language . . .

When you get in the pool, your body shoves some water out of the way to make room for you. Let’s say you could collect all the water your body moved out of the way and weigh it. Now, pretend that you lie down on the ground and have someone put all that water on top of you. You would feel the water pushing down on your body, right? That push you feel is a force. So, when you get in the swimming pool, the water you move out of the way starts pushing back. But instead of it pushing down on you, it pushes up trying to push you back out of the water. That force of the water trying to push you back out of the pool is called buoyancy!

Relate Archimedes’ Principle to what your child “feels” while in the pool. You feel lighter in water than you do out of the water because the water is actually pushing up on you . . . holding you up a bit!

If your child is able to understand the basics of Archimedes’ Principle, go a step further with the concept. If the weight of the water displaced is more than the weight of the object, the object will float. If the weight of the water displaced is less than the weight of the object, the object will sink. Ask them to explain why they sink in the water (when they don’t swim), but float when they lay on a float.

Finally, if your child swims well enough to “dive” for objects underwater, introduce a challenge. It’s them against the water! When they try to go underwater to get a object at the bottom of the pool, the water is trying to push them back up. The challenge? Who is stronger, you or the water? 🙂

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Teaching Kids about Consumerism and Conservation

Teaching Kids about Consumerism and Conservation

Let’s face it, the advertising world targets your kids every day. What child hasn’t been disappointed after saving for months for a toy, only to find it doesn’t measure up to what the commercial promised? In my science classes I teach my students how science can be used to objectively test claims made by advertisers . . . in other words, how to be wise consumers. Here’s a fun idea that actually came from one of my students. It combines a lesson about consumerism, along with a lesson about conservation.

Design an experiment to test which is more cost efficient, using disposable or rechargeable batteries. I’ll list some of the variables to consider below, but your child can easily design this experiment themselves for some hands on practice using the scientific method.

1. Pick comparable battery brands to test. If you pick a name brand disposable battery, don’t compare it to a cheap store brand rechargeable, etc.
2. Use the same size battery of each type.
3. Test the battery life in the same way. An example would be using the battery to run any small electronic device. Measure the time the device remains in operation. Use the same device for both types of batteries, and keep the device under the same conditions (temperature, volume, etc.)
4. Decide on exactly what you’re comparing. Are you comparing the amount of time each battery will keep the device running? If so, you may want to also test different brands of each type. Are you trying to determine which type (disposable vs rechargeable) battery costs less in the long run? In that case, you’ll need to also factor in how many times the rechargeable can be recharged vs how many disposable batteries would have to be purchased to get the same result.

Again, those are just some suggestions of things to consider when designing the experiment. Your child will have plenty of ideas of their own. Gently guide them into using the scientific method to design their experiment so their results are valid.

Extensions of this lab are limitless! Older students can research the amount of waste produced by batteries or the amount of nonrenewable resources are used in the manufacturing of batteries. Find battery commercials or ads for the different brands and types tested. Challenge students to evaluate the claims made by the manufacturers based on the results of their experiment. This will usually lead to a discussion about the accuracy of claims made about other products. Encourage your child to select several products that are commonly used in your home and put them to the test! Teaching kids not to believe everything they see and hear from the media, and teaching them that they have the power to evaluate these claims for themselves is a valuable life lesson!

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Slinky Waves

Slinky Waves

Have an old slinky collecting dust in the kids’ toy box? Pull it out and teach a quick lesson on the two types of waves.

1. Loosely stretch the slinky across the floor or long table with you holding one end and your child holding the other.

2. Create a transverse wave by shaking one end of the slinky horizontally across the floor or table. Continue shaking back and forth to set up a series of transverse waves that will move from one side of the slinky to the other.

3. Have your child identify the crests and the troughs of the waves.

crest and trough

4. Also explain that in a transverse wave the energy moves perpendicular (at right angles) to the motion of the medium. They can see the medium (the slinky) move side to side while they feel the energy being transferred from your hand to theirs. Help them to see that the motion of slinky and energy are in different directions.

5. To make a longitudinal or compression wave, make a quick shoving motion with the slinky toward the person at the other end. You should be able to see a compression travel along the slinky between your hand and the person on the other end. Continue making compression waves in the slinky for your child to observe.

6. Have your child identify the compression and the rarefaction (see below).

compression and rarefaction

7. Explain that in a longitudinal or compression wave the energy moves in the same direction as the motion of the medium. In this case, they should see that both the slinky and the energy from your push are both traveling in a straight line between your hand and theirs.

If you are trying this with small children it may be difficult for them to identify the motion of the medium vs the energy. At lower grade levels, just focus on the fact that there are two different kinds of waves and how they look different. If your child is ready for new terms, help them identify the parts of one or both types of waves.

Finally, for all children, extend the lesson to brainstorm where they have observed (or how they can make) transverse and longitudinal waves in different types of media (water, rope, air, etc.)

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Outdoor Activity Explains Energy and Work

Outdoor Activity Explains Energy and Work

Energy is defined as the “ability to do work.” Energy and work are really different forms of the same thing, but to a child, they are very different. Try this simple outdoor summer activity to demonstrate the relationship between gravitational potential energy and work.

First, children need to understand gravitational potential energy. Explain to your child that a ball on the floor has no potential energy because it won’t move by itself. But, a ball on the edge of a shelf has potential energy because it can fall off of the shelf. While the ball is moving, it has energy. While the ball is sitting on the shelf it has “potential” energy because it has the “potential” to fall.

Children also need to know that the scientific definition of “work” is moving an object through a distance. The larger the object and the farther the object is moved, the more work is done on the object.

Next, explain to your child that energy is “the ability to do work.” Relate this to the ball sitting on the shelf. When the ball falls off the shelf and hits the ground, will it do work? (Technically, the answer is yes. The ball will transfer energy to the molecules in the floor, causing them to heat up slightly. But, this is not something that can be easily explained or understood by a child!) The following activity will help your child answer the question.

1. Place a pan of water on the sidewalk or driveway so water splashing out can be easily observed and/or measured.

2. Use a ball that has enough weight to make a splash when dropped into the pan of water. Raise the ball 1 foot above the surface of the water. Drop the ball into the water and observe.

3. Small children can observe how far the water splashes, or mark the farthest splash with sidewalk chalk. Older children should measure the distance from the edge of the pan to the farthest splash and record.

4. Fill the pan if needed. Repeat the ball drop from a height of 2 feet. Observe, mark, or record how far the water splashes from the pan.

5. Continue several more trials so that your child can observe that the higher the height of the ball, the farther the splash.

Now, relate the activity to the concepts of energy and work. When the ball is held above the water, the ball has potential energy. The higher the ball is held, the more potential energy it has. When the ball is dropped, the potential energy is released and the ball moves. (Technically, the potential energy is converted into kinetic energy, or the energy of motion. You may want to introduce this added concept with older children.) When the ball hits the water, the energy from the ball is transferred into the water, causing the water to splash out of the pan. Since the water is moved through a distance, the ball does work on the water. The more potential energy the ball started with, the more work it does on the water, and the farther the water can be moved.

To extend the activity and allow your child to use up some of their own potential energy, encourage them to experiment with “adding energy” to the ball by throwing it into the water to see how far they can get the water to splash!

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Make Waves in the Tub

Make Waves in the Tub

Light waves . . . sound waves . . . it’s all pretty hard for a younger elementary student to understand. They can see light and hear sound, but the wave part just isn’t something they can perceive with their senses. A good way to begin to introduce the topic of waves is with water waves. A wave that is visible and moves slowly enough for them to observe the actual wave itself.

Use bath time as a way to introduce the topic of waves to your younger child. Here are some basic wave properties that can be observed in the tub:

1. Have your child make a series of waves in the water and observe. The highest point in a wave is called the crest. The lowest point is the trough. As you make waves toward your child, have him/her point out or try to catch a crest and a trough.

2. The distance between the crest of one wave and the crest of the next wave is the wavelength. Have your child experiment to find a way to make waves with a long wavelength and then with a short wavelength. Talk about what determines the size of the wavelength. (How fast the child moves determines the wavelength. All waves are caused by vibrations. The speed of the vibration determines the wavelength.)

3. The distance between the height of the crest and the midpoint of the wave (the water level if there were no wave) is the amplitude. Have your child experiment to find a way to change the amplitude of the waves. Talk about what determines the size of the amplitude. (Amplitude is actually determined by the amount of energy in the wave. The more energy your child puts into making a wave, the larger its amplitude will be.)

Through this bath time activity, your younger child will learn the basic parts of a wave and two fundamental wave properties. And, they will be a little cleaner, too! 🙂

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Understanding and Measuring Friction

Understanding and Measuring Friction

For elementary children, the topic of “opposing forces” can be hard to understand. Friction is an opposing force that children can “feel.” Here’s a lab on measuring and comparing friction that’s appropriate for older elementary children. You will need one piece of “science equipment” to get the most out of the lab . . . a spring scale. A spring scale with small increments will be easier for elementary children to use.

Here’s what to do:

1. Find an object that can be easily hooked onto the spring scale, that is fairly heavy (but will still read when hung from the spring scale), and preferably with a large, flat surface. A heavy block of wood with a cup hook works very well.

2. Have your child hook the object onto the spring scale and drag it across the smoothest possible surface you can find. While dragging the object slowly, have your child read and record the amount of force they are using to move the object. (Newtons is a measure of force, so the part of the scale marked as “N” is actually a measure of force.)

3. Next, have your child hunt for 5 different surface with as many different textures as possible. The surfaces must be large enough to drag the object across, just as was done in step 2.

4. Ask the child to predict what will happen when they drag the object across the different textured surfaces. They will most likely come to the conclusion that some surfaces will be harder to pull across than others. Ask them to come up with an explanation for WHY this is true.

5. Introduce the topic of “friction” by explaining that friction is a force that acts in the opposite direction from the force you apply to move an object. When they drag their object one way, the surface tries to pull it the opposite way!

6. Now, have your child predict which of their selected surfaces will pull more than others. Have them rang the surfaces in order from least friction to more friction.

7. Finally, it’s time to test their predictions. Have your child drag the object in the same way across each of the different surfaces. As they are slowly dragging the object, they should read and record the force they must use to pull the object.

8. Subtract the force needed to pull the object on the smooth surface from the force needed to pull it on each of the textured surfaces. This is a measure of how much more force the textured surface was putting on the object. The larger the number, the more friction force was applied by the surface.

To put it all together, remind your child that a force is just a push or a pull. So, when they put a force on the object in one direction, the surface will put a force on the object in the opposite direction. The more force applied by the surface, the harder they have to pull to get the object to move.

As an extension, relate this topic to the practical chore of moving a heavy object. Have them brainstorm ways that can be used to make sliding a heavy object easier.

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Calculate Speed While Encouraging Exercise

Calculate Speed While Encouraging Exercise

We all know that kids have a lot of energy. Put that energy to good use by combining a physics lesson, a math lesson, and some good exercise! All you’ll need is an energetic kid, a tape measure, a stopwatch, and a safe place for your child to run.

Calculating Speed

1. Pick out a “track” that your child can run safely. Select a distance appropriate for your child to run several times.

2. Help your child measure the distance of the selected track with the tape measure. You can measure with any units: yards, feet, meters, etc. Have your child record the track distance.

3. Measure the time it takes for your child to run the selected track. If possible, measure the time in seconds. Record.

4. Introduce the formula used to calculate speed:  speed = distance / time

Depending on the math level of your child, help them calculate their speed by dividing the distance of the track by the time it took to run it. Older children can calculate speed using long division. For younger children you may want to introduce the usefulness of technology by showing them how to get their answer with a calculator.

5. Repeat the run with the same track, or a different one as long as your child is interested and energetic. Challenge them to improve their speed with each run.

As an extension of the lab, students can compare their speeds when a) wearing different types of shoes, b) running on different surfaces, or c) running courses of different lengths. Any of these options will increase your child’s interest in the lab, as well as give them extra practice with division . . . and a little more exercise!

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