Types of Interactions and How to Detect Them: Difference between revisions

Revision as of 21:24, 15 April 2016

Claimed by Julia Clendenin

Short Description of Topic

Interactions and How to Detect Them

Simply, interactions occur when one object comes into contact with another object or a force that alters its original behavior. A force is an energy that results in an action by some object, and is often calculated as mass times acceleration. Alternatively, interactions can be described as changes to the system as a result of the surroundings (external forces) or interworking of the system (internal forces). It is important to note that object and system are interchangeable, although system is the physics term more appropriately used. The system is the point of focus and is interacted upon or within itself. The surroundings refer to any outside forces that interact with the system.

Depending on the type of force, different equations are used to calculate the interactions within a system. Generally, force can be described as [math]\displaystyle{ {\frac{d\vec{p}}{dt}}_{system} = \vec{F}_{net} }[/math] where m is the mass of the system in kilograms (kg) and a is the acceleration of the system.

Detecting Interactions

Since interactions alter the behavior of the system, there are several indicators that express any deviation: change in velocity, change in direction of motion, change in energy, uniform motion.

Change in Velocity

Suppose an object is at rest, or its velocity is equal to zero. Just from this simple statement, we can infer that at least two interactions have occurred: 1) an interaction is holding it in place, or preventing it from moving, 2) two interactions are oppositely acting upon the object, thus canceling each other out. Let's break down each one for clarity:

1) An interaction is holding it in place, or preventing it from moving. Look at your desk. You probably have a calculator, a GT Infinite Harmony concert ticket, and pens sitting idly before you. Why aren't they moving? This lack of movement indicates some interaction occurring with each object. One such interaction is a gravitational interaction. As gravity pulls downward on your calculator, it stays on your desk instead of flying upwards (if only gravity didn't interact on our GPAs!). These objects exhibit an interaction because they are not moving where otherwise they could be. Another potential interaction is friction. While you'll delve deeper into friction and its intricacies later, for now, friction keeps objects from slipping (or moving). Look at your coffee mug on its coaster. It isn't sliding off the coaster because friction is keeping it in place.

2) Two interactions are oppositely acting upon the object, thus canceling each other out. The interaction from the left plus the interaction on the right equate to zero, resulting in no movement from the object locked in the middle.

Suppose the object moves in the positive x direction, and then comes to rest. Which of the following could be the cause for the object's change in velocity?

a) an interaction in the +x direction is reduced

b) an interaction in the -x direction is reduced

c) an interaction in the -x direction is increased

d) an interaction in +y direction is applied

e) an interaction in the -y is applied

f)

Let's dissect each option. If an interaction from the +x direction is reduced, the object can continue to move at a constant velocity; just because the original interaction changes does not indicate that the system will cease to act. Thus, choice a) is incorrect. An interaction from the -x direction does influence the velocity of the system as it is acting in the opposite direction of the system's initial velocity. However, if the -x interaction is reduced, the force preventing the object from moving is lightened and the velocity reaches a constant; it does not necessarily stop, and choice b) is incorrect. If the interaction in the -x direction is emphasized, then the object's velocity will slow and then stop as the interaction increases to a point that overcomes the initial velocity of the object; answer c) is correct. For both choices d) and e), since the object is moving in the x direction, the y interactions do not directly influence the x-direction velocity, thus both are incorrect.

Change in Direction of Motion

Purpose and Application

How do we visualize or predict using this topic. Consider embedding some vpython code here Teach hands-on with GlowScript