NCERT Exemplar problems friction notes pdf free download its answers are also available to download. Solutions of all questions are described completely.
Every thing is given as separate PDF files. Assignments, Notes, Sample Papers, Chapter test and other study material will be uploaded very soon. Please give feedback and suggestions to improve the contents and quality if possible. Important questions for exam will be uploaded next week. A block and tackle is a system of two or more pulleys with a rope or cable threaded between them, usually used to lift or pull heavy loads. The pulleys are assembled together to form blocks and then blocks are paired so that one is fixed and one moves with the load. The rope is threaded through the pulleys to provide mechanical advantage that amplifies the force applied to the rope.
Hero of Alexandria described cranes formed from assemblies of pulleys in the first century. Illustrated versions of Hero’s “book on raising heavy weights” show early block and tackle systems. Various ways of rigging a tackle. A block is a set of pulleys or “sheaves” mounted on a single frame.
An assembly of blocks with a rope threaded through the pulleys is called tackle. A block and tackle system amplifies the tension force in the rope to lift heavy loads. They are common on boats and sailing ships, where tasks are often performed manually. Luff tackle and Gyn tackle have mis-matched blocks with differing numbers of pulleys. A block and tackle is characterized by the use of a single continuous rope to transmit a tension force around one or more pulleys to lift or move a load. Its mechanical advantage is the number of parts of the rope that act on the load.
The mechanical advantage of a tackle dictates how much easier it is to haul or lift the load. If frictional losses are neglected, the mechanical advantage of a block and tackle is equal to the number of parts in the line that either attach to or run through the moving blocks—in other words, the number of supporting rope sections. The mechanical advantage is 2, requiring a force of only 50N to lift the load. Consider the set of pulleys that form the moving block and the parts of the rope that support this block.
The mechanical advantage is three, the increased force produced by a tackle is offset by both the increased length of rope needed and the friction in the system. If frictional losses are neglected — requiring a force of only 25N to lift the load. They are common on boats and sailing ships, in this case the block and tackle is said to be “rove to advantage. By adding a pulley to the fixed block of a gun tackle the direction of the pulling force is reversed though the mechanical advantage remains the same, hero of Alexandria described cranes formed from assemblies of pulleys in the first century. An assembly of blocks with a rope threaded through the pulleys is called tackle. Reeving to advantage enables the pulling force to be in the direction of the load movement, nCERT Exemplar problems and its answers are also available to download. Luff tackle and Gyn tackle have mis, ideal mechanical advantage correlates directly with velocity ratio.