# Hands-On-PhysicsMECHANICS

## - Unit Overview -

### Background

Humans use a lot of effort transporting material from one point to another. Better techniques may be developed to reduce the time and energy spent moving stuff. A clear model for motion is helpful as a basis for design work on this problem. A mathematical model for an object pushed by a single constant force is central to the study of motion. Models for multiple forces and changing force are possible once single force motion is modeled. In this unit you will build an aircart, decide what attributes of the cart are pertinent, and what variables are important for the description of motion. You will decide how the variables are related. Determining a set of variables along with the relationships between them is the primary work of creating a model. A good mathematical model can be generalized and extended. With a good model in hand, design work can proceed.

### Goals

Understanding and controlling motion requires knowing some important physics that is central to this unit. We start by learning how to measure speed and then go on to see how force effects speed. As the unit unfolds, you are introduced to the major concepts of force and motion that are usually taught in physics, but through a series of interesting projects.

By the end of this unit, you should be able to:
• Use a ruler and a stopwatch to make the measurements necessary for determining speed, and to calculate an average speed from these measurements.

• Compare forces using a stretched spring

• Use the various units commonly used for speed, energy, and power.

• Design, construct, describe, and evaluate, a model air-propelled vehicle.

• Describe the factors that influence motion and relate speed to values of these factors.

• Give operational definitions of force, energy, and power

• Determine power output in both electrical and mechanical terms

• Quantitatively evaluate power efficiency

• Evaluate the transformation and use of energy in systems that involve motion.

### Learning Strategies:

Learn by Doing
Most people learn concepts by making things and then thinking about them. Too often students try to jump ahead and memorize the equations and definitions without giving themselves time to think. This is why Hands On Physics units emphasize "hands on" building.

HOP Structure
There are three major sections to each unit: "messing around," a "core project," and then "extensions." The "messing around" part is a chance to learn the big physics concepts without worrying about a lot of details and computations. The "core project" is an extended construction project that everyone does. Then you choose one of a number of "extensions" to work on.

Think in Lab
It is important that you use your mind while you are in the lab doing these various projects. You cannot just follow the directions and fill in the blanks. We don't tell you every little step because you should be learning how to do things yourself. Eventually, we want you to be able to undertake an entire project. To get to this level, you have to make larger and larger steps without help.

Fill in the Gaps
You may find this frustrating. You may get mad at the instructions that seem vague and you may wish your teacher could help you all the time. But before asking for help, talk it out in your group; try to invent a way out of your problem. If you are not sure whether you are doing the "right thing", write down what your problem was and what you decided.

Make Mistakes Rapidly
Remember, it is okay to make mistakes; we learn from our mistakes. Always think about safety and try to avoid breaking things. But if you make a mistake, don't be discouraged; just try again. The more mistakes you make, the more you must be learning.

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