Describing One-Dimensional Motion

1. In the animation to follow, you see two scenes, one followed by another. In which of the two scenes, if either, are the laws of physics violated?
   

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2. A ball is tied to a thin string which has one end tacked securely to table. The ball and string sit on the horizontal, frictionless table. The image below shows the view from above as the ball travels in a circular path. A razor blade is placed so that it cuts the string as shown in the image.
   

   After the string is cut, the velocity of the ball will have a direction shown below by arrow

   1. 
   2. 
   3. 
   4. 
   5. none of the above

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3. In the figure below you see a frictionless track which has an inclined section and a horizontally flat section. The blue ball, initially held at rest, is released and slides down the incline.
   
   As it slides, at some time the ball passes between points a and b. Still later, the ball passes between points c and g. Both points a and b and c and g are separated by a distance d. Neglecting any air resistance, is the time it takes for the ball to go from a to b
   1. greater than the time needed to go from c to g
   2. less than the time needed to go from c to g
   3. the same as the time needed to go from c to g
   4. impossible to compare to the time needed to go from c to g without a measurement
   5. dependent on the weight of the ball
   
   The solution to the above is here.

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   Discovered connections among seemingly very different observations of nature lead to the conclusion that physical reality is explainable by just a few(?) principles. Although we sometimes use the phrase "law of physics" when we mean "principle", laws describe mathematical relationships between quantities defined by principles. A principle, then, makes a very general statement about the way the universe works and this provides the "connection" between very different physical phenomena. The "connections" are usually discussed in terms of laws or theorems and the discussion takes place principally in the language of mathematics. What's important to remember is that the principles and laws reflect observations of the way the world works, not thinking uninformed by experiments.

   Sometimes these connections are very far-reaching. For example, the same principles of physics inform us about phenomena as different as

   1. Pool balls colliding

   2. Galaxies colliding

   3. Extinction of the dinosaurs

   4. Molecular dynamics

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   1. A bus slows with constant deceleration from 24 m/s to 16 m/s and moves 50 m in the process.
      1. How much further does it travel before coming to a stop?
      2. How long does it take to stop from 24 m/s?

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