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Machines 1. Machine : It is a device, by which we can overcome resistance, or gain speed by applying comparatively small force, at a convenient point, and in a desired direction. 2. Input : Work done on a machine or energy supplied to a machine is called input. 3. Output : Work done by a machine or energy produced by a machine is called output. 4. Actual Output : The total work done by a machine is called actual output. It includes the work done in moving the parts of the machine and the friction. 5. Useful Output : The useful work done by a machine is called useful output. It does not include work done in moving the parts of machine and the friction. 6. Ideal Machine : A machine whose parts are weightless and frictionless, is called an ideal machine. 7. Mechanical Advantage or Actual Mechanical Advantage : The ratio between the useful load (resistance overcome) moved by a machine, to the effort applied on it is called mechanical advantage or actual mechanical advantage. 8. Ideal Mechanical Advantage : The ratio between the total load moved, inclusive of the friction and the movable parts of a machine, to the effort applied on it is called ideal mechanical advantage. Class-X 1 Key points 9. Velocity Ratio : It is the ratio of the velocity at which an effort is applied to the velocity at which the load moved. or It is the ratio of displacement of the effort to the displacement of the load. 10. Efficiency of Machine : It is the ratio between the useful output to the actual input of a machine. or It is the ratio of the mechanical advantage and the velocity ratio of a machine. 11. Lever : It is a straight or bent rigid bar, capable of turning around a fixed point or an axis, commonly called fulcrum. 12. Lever of 1st Order : A lever, in which the fulcrum acts in the middle, the load at one end and the effort at the other end, is called a lever of 1st order. 13. Lever of 2nd Order : A lever, in which the load acts in the middle, the fulcrum at one end and the effort at the other end, is called a lever of second order. 14. Lever of 3rd Order : A lever, in which the effort acts in the middle, the fulcrum at one end and the load at the other end, is called a lever of third order. 15. Principle of Lever : When a lever is in equilibrium : Load Load arm = Effort Effort arm. Class-X 2 Key points 16. Pulley : It is a flat circular disc, having a groove in its edge, and is capable of revolving around a fixed point passing through its centre and commonly called axle. 17. Single fixed pulley system : When a single pulley fixed at a higher platform is used to raise a load or change the direction of effort, it is called single fixed pulley system. 18. Single movable pulley system : A system of two pulleys, such that one of the pulley is fixed at higher platform (fixed pulley) and the other pulley is attached to load (movable pulley), such that movable pulley rises up or down along with the load is called single movable pulley system. 19. Block and Tackle or Sheaf Pulley System : A system of two sets of two or more pulleys mounted on the same common axle, such that one set is fixed on a higher platform (commonly called block) and the other set is connected to load (commonly called tackle) is called block and tackle system. 20. Inclined Plane : A smooth flat rigid surface, inclined at some angle to the horizontal surface is called an inclined plane. Class-X 3 Key points
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