- Physics Planet
- Tuesday February 21, 2017

The definition of “kinematics” is the study of the motion of objects using words, equations, graphs and diagrams and numbers. Kinematics is a study aimed at explaining the motion of objects.

The “Kinematic Equations” all have four variables. If you know three of the variables then you can always calculate the fourth. These equations can help us understand and predict an object’s motion. The four equations use the following variables; displacement of the object, the time the object was moving, the acceleration of the object, the initial velocity of the object and the final velocity of the object.

These two basic concepts are fundamental building blocks to understanding physics. Speed and velocity are not the same thing. Speed is defined “how fast an object is moving”. An object that is not moving has no speed. Something moving very fast would have high speed and then it follows that a slow moving object would have low speed.

Velocity is defined as “the rate at which an object changes its position.” Think about a driver of a car that drives ahead ¼ of a mile and then the driver puts the car in reverse and drives back ¼ of a mile – each time going back and forth and each time returning to the original starting position. The movement of the car would never change position and therefore it would have zero velocity.

If the driver wanted to maximize the car’s velocity, then the driver should drive the car as far from the original starting point in order to maximize the amount that it is displaced from the original position, trying not to change directions or make any turns.

Speed is known as a “scalar quantity” and Velocity is known as a “vector quantity”. Scalar quantities are defined by magnitude alone, while vector quantities are defined by magnitude along with a direction.

Distance and displacement are two basic concepts that can also be easily misunderstood. Distance is a scalar quantity that is described by magnitude, and displacement is a vector quantity describing how much an object moved; in other words, the change in position.

To test your knowledge of this concept, consider a man who walks 1 mile North, 2 miles East, 1 mile South and 2 miles West. The man would have walked 6 miles (distance) but his displacement is 0 miles. In this example, the 1 mile North and South cancel each other out and the 2 miles East and West also cancelled each other out and the person returned to the starting point.

Acceleration is another concept that you will need to get a handle on. Many people misunderstand the meaning of acceleration. Some people think that it means that something or someone is moving fast. However, you can have an object or a person moving really really fast and yet not accelerating. To be accelerating, an object or person would have to change its velocity.

Constant acceleration occurs when an accelerating object or person is changing its velocity by the same amount per a time frame; like a second, for instance. The velocity is changing by the exact same amount for each second. Again be careful here. An object or person with a constant acceleration is not the same thing as a constant velocity. An object or person with a constant velocity is not accelerating.

For objects that have a constant acceleration, the distance traveled is directly proportional to the time of travel squared. Remember that this is for objects that have a constant acceleration. So if an object travels twice the time, then the object will go four times the distance, this continues for three times the time the distance traveled will be 9 times the distance and four times the time then it will have traveled 16 times the distance.

For objects that are accelerating but not at a constant rate you can calculate the average acceleration by taking the change in velocity divided by the time. Acceleration is usually depicted by units per time units; the ones that are used most frequent would be m/s/s, mi/hr/s, km/hr/s.

Remember that acceleration has a direction associated with it and therefore is called a vector quantity. The actual direction of the acceleration vector is dependent on whether the object is going faster or going slower and whether the object is traveling in the positive or negative direction.

The animation industry is one modern day job that uses kinematics. For animated movies including 2-D and 3-D animations, physics, especially the study of motion or Kinematics is important. So, keep studying physics and you may end up with a hot job in Hollywood.

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