The video provides a basic summary of Newton’s Laws of Motion and Forces. The video first starts with a basic question, “What is it that causes an object to speed up?” The answer given is that “force” is the only thing that can cause an object to accelerate. The video uses a number of different examples to illustrate how motion and force operate in the physical world. This brief paper will provide a summary of the video, along with explanations of the concepts provided.
In the first illustration, a wooden apple is shown on a marble table and the narrator discusses how most people make assumptions about how various properties of the apple and the marble table (e.g., the apple is light and smooth and the table is more rough and heavy). He goes on to say that most people also make assumptions about how the apple would move if it were hit to one side. He then poses a question, “What if we remove all of the air in the room which could cause “air resistance,” remove all of the friction from the ground and walls, and remove the force of gravity?” The apple is then picked up with a clamp and released, but this time it does not move and staying in the air. This is because there are no forces acting upon the apple. Interestingly; however, if the apple is bumped while suspended in the air, it continues to move at the same velocity (in a straight line until it is hit again). This phenomenon is very similar to what happens to objects in outer space.
The video then provides a brief history about Sir Isaac Newton’s (whilst a picture of Galileo) Laws. First, his three Laws of Motion are introduced. The First La states, “An object with constant position, or constant velocity will remain at that position or velocity unless acted upon by a net external force.” This corresponds to what was said in the beginning of the video.
Newton’s Second Law states, (F = m*a). This means that in order to speed up an object by a certain amount, the force will need to be adjusted depending on the mass of the object. When one variable is held constant, then the others can be figured out using the simple formula. For example, if the same force is used on two objects, the lighter (one with less mass) object will accelerate at a faster rate than the heavier object. The video provide provided an interesting (and clear) explanation of why a feather and a hammer dropped from the same height will hit the ground at exactly the same time. The explanation is simple: if the masses are different and the acceleration is the same, then the force of gravity that acts upon the hammer is more than that on the feather (the ratios of force to mass are equal). The narrator also points out that there is a difference between the weight of an object (i.e., Fg = “force of gravity acting on an object”) and mass of an object (which is a quality that never changes). The formula, Fg = m*ag can be used to find the weight of an object from its mass (or vice versa).
Newton’s Third Law states, “For ever action force there is an equal and opposite reaction force.” For example, as a person sits on a chair and exerts force onto that chair, that chair equally exerts force back onto the person. The video also states that this is the reason that people are able to walk forward, because shoes put force onto the ground and the ground puts force back onto the shoes.