Posts Tagged ‘Christian Kids Explore Physics’

The Speed of a Rotating Cookie

Monday, August 29th, 2016

speed-of-a-rotating-cookie

Today we are baking a gigantic cookie, and then we will spin it! We are attempting to determine the speed of a rotating cookie, and I will compare it to a merry-go-round.

First you need to go into your kitchen and bake a huge chocolate chip cookie.

baking-cookiesThis post contains affiliate links. I was compensated for my work in writing this post.

You can use your favorite cookie dough recipe. My daughter Rachel tells you how much of each ingredient she used to make her cookie:

This fun experiment is from Christian Kids Explore Physics by Bright Ideas Press, In the chapter on motion, the book describes how to figure out the speed of a merry-go-round. First you need to determine the circumference of the merry-go-round.

C = 2π r

The radius of the merry-go-round is 5 feet.

5 times 2 times 3.14 equals 31.4 feet. So the distance around the merry-go-round is 31.4 feet. That means every time Rachel goes around, she travels 31.4 feet.

Now we need to determine how fast the merry-go-round is going. My son pushed Rachel around as hard as he could while my other son timed 15 seconds. I counted how many times Rachel went around in 15 seconds. The answer was almost 4 times–3.75 times is more accurate, as you can see if you watched the video. 3.75 times 4 equals 15 revolutions per minute. (A minute has 4 segments of 15 seconds.)

To determine how many feet Rachel traveled in one minute while riding the merry-go-round, multiply the circumference by the speed. She traveled 471 feet per minute!

merry-go-round-physics

In the video I show you how to determine the speed of your rotating cookie at home, depending on how big it is and how fast you spin it. Who knew physics could be so fun and delicious!

Turning Potential into Kinetic Energy

Monday, August 22nd, 2016

turning-potential-into-kinetic-energy

In today’s experiment, we will be turning potential into kinetic energy as we hold various objects above a bucket of water and release them to see how far they splash.

Sounds fun, doesn’t it?

You will want to do this experiment outside on a sunny day. The person dropping the objects needs to be willing to get wet, especially when the person releases the heavier objects like the banana and the can of baked beans!

Turning Potential into Kinetic Energy (The Experiment)

Step 1: Gather supplies. You will need a large tub, a hose, a ruler, and various objects to drop into the water. We used a marshmallow, a grape, a nut, a quarter, a pine cone, a banana, and a can of baked beans.

splashing-experimentThis post contains affiliate links. I was compensated for my work in writing this post.

Step 2: Fill the tub with water and have someone hold a ruler on the side of the tub. Print out the chart on page 143 of Christian Kids Explore Physics by Bright Ideas Press, and clip it to a clipboard. Record your findings on the chart, or you can just call out how many inches the water splashed upwards.

splash-grape

Step 3: Drop each object and watch how far the water splashes. The objects with more mass have more potential energy. When an object is held above the water, there is potential energy in the object. Potential energy is converted into kinetic energy as soon as you release the object because it is now moving.

Let me describe it another way: A log of wood has potential energy. It’s just sitting there and doesn’t look like it has energy, but as soon as you light it on fire, the potential energy is converted into kinetic energy.

Energy will be released if something happens to an object with potential energy. As long as an object just sits there, it’s only potential. When movement or chemical change occurs, you now have kinetic energy.

Video of the Splashing Experiment:

Take a look at how far each of our objects splashed:

Hope you enjoyed our fun experiment!

Changing the Coefficient of Friction

Monday, August 15th, 2016

changing-the-coefficient-of-friction

Today we are doing an experiment about changing the coefficient of friction. We will be swooshing a penny and a book across an unpolished table. Then we will polish the table and try it again.

Friction is resistance that keeps an object from moving forward. As you can see in the video, our coffee table has seen better days–it is battered and has lots of tiny grooves and dents. This provides a surface that is full of friction to cause a penny or book to slow down while being slid across a table.

How to do the friction experiment:

sliding-pennyThis post contains affiliate links. I was compensated for my work in writing this post.

This is how we conducted this friction experiment from Christian Kids Explore Physics by Bright Ideas Press:

Step 1: We slid a penny and a book across an unpolished table. We noticed that the penny got stuck as it didn’t want to slide across a table full of nicks and dings.

Step 2: We polished the table with furniture polish. Using a soft rag worked better than using a paper towel, as far as shining the table. The reason the table never looked visibly shiny is that there was no varnish left on the poor coffee table. Even then, the table became more slippery when polished.

waxing-table

Step 3: We slid the penny and the book across the polished table. This time we noticed that the penny had less friction as it slid across because there were fewer obstacles slowing it down.

My kids went next door to slide the penny on the neighbor’s waxed wooden floor. The penny slid around with way more speed! Even the neighbor’s dog had trouble walking on such a frictionless surface!

Then my husband polished one side of the coffee table and not the other, and there was a visible difference in speed when he flicked two wooden coins across the table. The polished side went noticeably faster and flew off the table!

Measuring the Magnitude of Force

Monday, August 8th, 2016

Measuring-the-magnitude-of-force

Today we are hanging some fruit from a chandelier and poking it with a straw–yes, we are measuring the magnitude of force!

Are you ready for a ridiculously fun experiment? You will need the following items: string, a chandelier or door knob, a bendy straw, tape, scissors, a grape, an apple, and a banana.

Here are the results of our experiment:

How to conduct the experiment:

Step 1: Make sure the fruit is completely dry before attempting to tape the string to the fruit. We used packing tape, but apparently flimsy scotch tape also works. I was shocked to see the banana didn’t fall and splat with weak scotch tape holding it up.

Step 2: Tie the other end of the string to the chandelier or door knob.

taped-grapeThis post contains affiliate links. I was compensated for my work in writing this post.

Step 3: Grab a bendy straw and push each piece of fruit. Notice that the grape does not bend the straw, but the apple and the banana require more force to move, so they bend the straw. The more mass an object has, the more force is required to move it.

laughing

The photo above is the moment I discovered the weak tape was holding the banana up. It was quite hilarious, since I was expecting a splat.

physics-force-elementary

See how the grape requires almost no effort to move, since its mass is so small. On the other hand, the other two pieces of fruit require more force to accelerate. To accelerate something means to make it move forward or change its velocity. We accelerated the speed of the fruit in this experiment while determining the magnitude of force required to move each piece.

hanging-fruit

This fun experiment is from the book Christian Kids Explore Physics by Bright Ideas Press. Why not pick up your own copy today!