: Dynamics

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Unit Activity: Dynamics

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Task 1

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Dynamic Model-Friction on Ice

physical situations.

Now that you know how forces affect the motions of objects, you can use the Tracker video analysis tool to create dynamic models for a wide range of

Tracker enables you to create two different types of mathematical models: analytical and dynamic. An analytical model enables you to enter

mathematical expressions for x and y positions as a function of time. That's sometimes useful, but from a physics perspective, a dynamic model is much

more flexible and powerful.

A dynamic model enables you to set the initial conditions for a particular system (initial positions and velocities); then you can mathematically define

any forces acting on that system. Once those are set up, the model acts like an object in space, responding to the forces you've imposed on it. It can

continue moving forever, if that's what the forces would do to an object in real life. By visually matching a marker for your model to the real motion on

the video, you can define and refine a mathematical model for a wide range of real-world situations.

In the first two tasks of this Unit Activity, you'll create dynamic models for motions in both one and two dimensions.

Activity Research - Creating a Dynamic Particle Model

Before you begin, do a little research and find out where you can get help in creating your models. In Tracker, you can always access illustrated help to

do anything. In Tracker, you can always access the illustrated Help dialog (? In the Toolbar).

For this project, you're going to need to check out the Tracker Help instructions for Dynamic Models. You can print this Help document, but it is

available from Tracker anytime you need to refer to it.

For this project, you're going to need to check out the Tracker Help instructions for creating a dynamic model.

Instructions - Building your Dynamic Model

Start your activity by opening this Tracker experiment: Ice Slide 2 model man

Click play _ to watch the video. The other video controls allow you to rewind (x] the video or step forward Di] or backward k one frame at a time.

In this activity, you'll define a dynamic model for the motion of an adult sliding on ice. In the Ice_Slide2_model, a blank model setup is already in place

for you. The file also has the man's motion tracked with point mass Ice Slide 2.

For this one-dimensional motion, the vertical force of gravity and the normal force balance out. Although there is some air drag, the only significant

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