Isaac Newton's Second Law of Motion
SVG - Scalable Vector Graphics Page
The Second Law is concerned with relating acceleration to mass and net force.
Acceleration is directly proportional to the applied net force.
SVG
Be sure that you notice:
- The masses, or objects, are the yellow rectangles. All of the masses are the same. So this demonstration does not consider any change in mass. The mass is constant.
- The applied net forces are the red arrows. The forces are not the same. The one at the top is the biggest, the one at the bottom is the smallest, and the one in the middle is medium sized.
- All of the objects accelerate. The velocity in each case gets greater and greater. That is, the speed increases. However, the three accelerations are not all the same. Every one speeds up, but they speed up differently.
- The acceleration at the top is the largest acceleration. The velocity changes by the largest amount per second here. Note that the largest force is applied to this mass. So the largest force has the largest acceleration.
- The acceleration at the bottom is the smallest acceleration. Here the velocity changes by the smallest amount per second. Also, here we have the smallest force. So the smallest applied force creates the smallest acceleration.
- And the medium sized force, in the middle, creates the medium sized acceleration.
- The middle force has one half (1/2) the size of the top force. The middle acceleration has one half (1/2) the size of the top acceleration. You probably can not see this perfectly without taking measurements, but the animation is programed to show it. The acceleration and force change by the same factor, and that is what is meant by a direct proportion between acceleration and force.
- The bottom force has one third (1/3) the size of the top force, and the bottom mass experiences one third (1/3) the acceleration of the top. Both force and acceleration change by the same factor; so, again, it's a direct proportion demonstrated.
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