# solid

States of Matter (video 3:48) – solid, liquid, gas

• States of Matter – Water can exist as a solid as in an iceberg. It can also exists as a liquid, such as the ocean. Finally, water can exist as a gas. We know this form of water as water vapor.

Solids – the first in the series of Engineering ideas that apply science in the transition to engineering.

Rigidity

Flexibility

During the design process, engineers select materials to use in their designs. These materials must be able to withstand the forces that the device or structure is expected to experience and must be compatible in the environment that the device or structure will operate in.

Mechanics of Solids uses concepts and knowledge of continuum mechanics emerging from physics and mathematics to understand and predict the behavior of solid matter under external actions, such as external forces, temperature changes, and displacement or strain. The principles are broadly used on a variety of topics for a number of engineering disciplines. It is part of a broader study known as continuum mechanics. Engineers use the principles to determine what happens when a stress is applied to a component. Concepts are useful anytime that a component departs away from the rest shape due to stress. The amount of departure from rest, which is initially elastic or proportional to stress, is safe as long as the material is below its yield strength. For example, an aerospace engineer would have used Mechanics of Solids extensively in the design of the Space Shuttle first launched on April 12, 1981.

Soft engineering (video 15:54) – involves manipulating and constraining the air pressure in flexible materials. The idea is already present in nature – Saul compares a bluefin tuna and a shark. The tuna’s tail wing is bony but the shark’s cartilage is lighter and stiffer. The shark can tune its stiffness to swim fast at high pressure and be very maneuverable at low pressures. Griffith shows examples of soft engineered robots gripping eggs, walking under walls, and pumping blood through a heart.
What’s the problem?
The materials that engineers select are key to the success or failure of designs. Questions correspond to the steps in the [/Engineering%20Design%20Process Engineering Design Process]. To ensure correct functioning, engineers must understand the properties of the materials selected for the device as well as the properties of the surrounding materials that the device will be interacting with.

• Ask – If a device is designed to function in the human body, then it must be biocompatible, survive any forces or chemicals that the body may impose on it, and not harm any part of the body.
• Imagine – There are plenty of man-made materials with properties like natural materials, as well as special properties that are “better” for the application than what nature provided.
• Design, Build
• Improve

That’s engineering

• matter – the substance of which a physical object is composed: something that occupies space and has weight (solid, liquid or gaseous)