## ASVAB Mechanical Comprehension Practice Test 268610

 Questions 5 Topics Block and Tackle, Force Lines of Action, Second-Class Lever, Structural Loads, Third-Class Lever

#### Study Guide

###### Block and Tackle

Two or more pulleys used together constitute a block and tackle which, unlike a fixed pulley, does impart mechanical advantage as a function of the number of pulleys that make up the arrangement. So, for example, a block and tackle with three pulleys would have a mechanical advantage of three.

###### Force Lines of Action

Collinear forces act along the same line of action, concurrent forces pass through a common point and coplanar forces act in a common plane.

###### Second-Class Lever

A second-class lever is used to increase force on an object in the same direction as the force is applied. This lever requires a smaller force to lift a larger load but the force must be applied over a greater distance. The fulcrum is placed at one end of the lever and mechanical advantage increases as the object being lifted is moved closer to the fulcrum or the length of the lever is increased. An example of a second-class lever is a wheelbarrow.