Newton’s 3rd Law vs. Algodoo

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his video shows two boulders of equal size, but different mass. When they collide, they each exert a force that is equal in magnitude to what the other exerts, but the reason that the lighter boulder gets pushed back farther is because it has less mass, so it has less inertia than the heavier one, which means that it will be pushed farther and faster than the heavier one.  

Transfer of Momentum vs. Algodoo

In this video we can see that there are two boulders of equal size, but different masses. The dark brown is wood, while the grey is stone. The lighter, wood one starts moving toward the heavier stone boulder, and when they collide the lighter boulder is forced backwards, while the the stone boulder starts moving in the other direction. We call this collision a transfer of momentum, which means that the momentum of the wood boulder is transferred to the stone boulder. Momentum can be transferred through many objects as well, like Newton’s cradle. It has many marbles in the middle and when one marble strikes against the side, the marble on the opposite side pops straight out because the momentum of the first marble is transferred through all the other marbles, but when it reaches the end marble, there is no other marble behind it to steal the energy that it just gained, so it pops straight out.

Momentum (Algodoo)

In this video, we can see that we have a boulder that is moving at a constant speed. This object has a value called momentum, and this object can only have this value when it is moving because of its equation. It equation is p=mv which means that momentum is equal to mass times its velocity, so when an object has 0 velocity, it has no momentum, but when this mass of 100 kilograms starts going about 18 meters per second, it suddenly has a momentum of 1800 kg*m/s. So we see that both the amount of mass and the velocity of an object affect its momentum.

A Favored Retreat

Lake Tahoe in the Summer.

In the summer we go up to the mountains to seek a respite from the heat that drives everyone indoors. My favorite place to go is Lake Tahoe. Every time we go there my mom says, “Look at how blue the water is!” Looking out over the surface of the water, I see a shiny, cobalt surface. Later, paddling out a little ways from the beach, I see the floor of the lake right under me, though it must be at least fifty feet deep. The water is cool, and has a gentle wake. White, soft and wet the sand is almost like dough. If we get to the lake early enough, morning fog is still hanging over the lake. It’s almost as though it clears the waters before humans arrive so that the water is always cold, clean, and blue, ready for us to cool off in it, and to admire God’s creation.

--Jonathan Todd