Cards | 10 |

Topics | Bridge Forms, Coefficient of Friction, Drag, Gear Trains, Gravitational Potential Energy, Joules, Mechanics, Pascal's Law, Structural Loads |

The six basic bridge forms are beam, truss, arch, cantilever, cable, and suspension.

Coefficient of friction (**μ**) represents how much two materials resist sliding across each other. Smooth surfaces like ice have low coefficients of friction while rough surfaces like concrete have high μ.

Drag is friction that opposes movement through a fluid like liquid or air. The amount of drag depends on the shape and speed of the object with slower objects experiencing less drag than faster objects and more aerodynamic objects experiencing less drag than those with a large leading surface area.

Connected gears of different numbers of teeth are used together to change the **rotational speed** and **torque** of the input force. If the smaller gear drives the larger gear, the speed of rotation will be reduced and the torque will increase. If the larger gear drives the smaller gear, the speed of rotation will increase and the torque will be reduced.

Gravitational potential energy is energy by virtue of gravity. The higher an object is raised above a surface the greater the distance it must fall to reach that surface and the more velocity it will build as it falls. For gravitational potential energy, **PE = mgh** where m is mass (kilograms), h is height (meters), and g is acceleration due to gravity which is a constant (**9.8 m/s ^{2}**).

The Joule (J) is the standard unit of energy and has the unit \({kg \times m^2} \over s^2\).

Mechanics deals with **motion** and the forces that produce motion.

Pascal's law states that a pressure change occurring anywhere in a confined incompressible fluid is transmitted throughout the fluid such that the same change occurs everywhere. For a hydraulic system, this means that a pressure applied to the input of the system will increase the pressure everywhere in the system.

A **concentrated** **load** acts on a relatively small area of a structure, a **static uniformly distributed load** doesn't create specific stress points or vary with time, a **dynamic load** varies with time or affects a structure that experiences a high degree of movement, an **impact load** is sudden and for a relatively short duration and a **non-uniformly distributed load** creates different stresses at different locations on a structure.