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Home Concept Builders 1D Kinematics Motion Diagrams Help Help 14

Motion Diagrams - Questions 14 Help

When the forces acting upon an object are balanced, the object will maintain its state of motion; that is, its velocity remains constant. If the forces are unbalanced, the object will either speed up or slow down. The reverse logic is also true: if an object has a constant velocity, then the forces are balanced. And if an object is speeding up or slowing down, the forces are unbalanced.

In Activity 3, you will have to construct a motion diagram for six different verbal descriptions. The second question is randomly selected from a set of three elgible questions, each of which describes the same type of motion. Here is one of the three versions.
 

Question 2:

A skateboarder is moving leftward with a constant speed.

Dot Spacing

This verbal description is of a constant velocity (or constant speed) motion. An object that moves at a constant speed covers the same distance each second. One would expect the distance between adjacent dots to be constant.
 

Velocity Vectors

There are two important questions to answer when selecting the set of velocity vectors. First, which direction do they point? And second, is the length staying constant, increasing, or decreasing? The first question is easiest to answer. Velocity can be thought of as speed with a direction. The direction of the velocity is simply the direction that the object is moving. The second question pertains to the length of the vector arrow and that is where the speed comes in. A constant speed motion will be represented by velocity vectors with constant length.
 

Acceleration Vectors

The first question to ask is: Is the object accelerating? Accelerating objects are either changing their speed or their direction. None of the objects in this Concept Builder are changing direction. But there are some speed changes among the six descriptions. If the speed is constant, then the acceleration is zero and there is only one choice of vectors that fits this description. Select it and you'll be successful.

The following pages from The Physics Classroom Tutorial provide additional information related to this topic:

Velocity versus Speed

Acceleration

Dot Diagrams (or Ticker Tape Diagrams)

Vector Diagrams

Concept Builder Teacher Notes Directions