Science 'N' us-5 final - School Books Publishers India

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3. The process in which water is allowed to stand for few daysso that heavier insoluble particles settle down is called :(a) sedimentation ✓(b) filtration(c) evaporation(d) distillation4. The hardest and non-porous layer of soil is :(a) topsoil(b) subsoil(c) bedrock✓(d) humus5. Which of the following is not a method of soil conservation?(a) afforestation(b) step farming(c) strong embankments (d) overgrazing6. Which of the following is an example of sedimentary rock?(a) pumice(b) limestone(c) basalt(d) marble7. Bauxite is an ore of :(a) aluminium✓(b) iron(c) copper(d) mercury8. During photosynthesis, light energy is converted into :(a) mechanical energy(b) electrical energy(c) sound energy(d) chemical energy9. Which of the following is a non-renewable source of energy?(a) wind energy(b) solar energy(c) fossil fuels energy ✓(d) hydroelectric energy10. Potential energy is a form of :(a) electric energy(b) mechanical energy(c) chemical energy(d) solar energy✓✓✓✓12.SIMPLE MACHINESExerciseA. Answer the following questions :1. What is a machine?Ans. A machine is a device that works in a more easier and faster way than aman could do. By using a machine, less effort and energy is needed tocomplete a task.2. What are simple machines? Name any two simple machines.Ans. In our daily life, we use many types of machines. All big machines aremade up of a combination of one or more simple machines. A simplemachine is a device that can do the following :•Help to lift heavy objects•Complete the work in less timeTwo simple machines :1. Lever 2. PulleyHorizon Press129Science 'n' Us - 1 to 5
3. Which are the three classes of levers? Explain.Ans. Lever is a simple machine.(a) First class lever : In this lever, fulcrum is in between the effort andthe load. The distance between the load and the fulcrum is always lessthan the distance between the effort and the fulcrum. e.g. handpump,see-saw, scissors, etc.(b) Second class lever : In this lever the load is in the centre of thefulcrum and the effort. e.g. wheelbarrow, nut cracker, bottle cap opener, etc.(c) Third class lever : In this lever, the fulcrum is at one end of thelever, the effort is in between the fulcrum and the load. e.g. forceps, icetongs,stapling machine, etc.4. What is a pulley?Ans. A wheel or set of wheels over which a rope or chain is pulled in order tolift or lower heavy objects.5. What is a wedge?Ans. A wedge is also a simple machine. A wedge has two inclined planestogether in the shape of a 'V' . Wedge is used for cutting and splittingthings. e.g. an axe, blade, knife, etc.6. What is the use of an inclined plane in our daily life?Ans. An inclined plane is a flat surface which has one end higher than theother. When an object is moved up an inclined plane, less effort isneeded than if you were to left it straight up, but you must move theobject over a greater distance. As staircase, etc.B. Choose the correct word from side box and fill in the blanks :1. When the fulcrum is in the middle, it is first class lever. compound2. Pulley is used to draw water from wells. effort3. An inclined plane is a slanted surface used to raise an object. fulcrum4. A third class lever has effort in the middle. pulley5. Compound machines are two or more simple machinesworking together.inclinedC. Separate the following into first class, second class and third class levers :see-saw, forceps, a pair of scissors, pliers, nut cracker, wheelbarrow,fishing rod, bottle cap openerAns. 1st class 2nd class 3rd classsee-saw nut-cracker forcepsa pair of scissors wheelbarrow fishing rodpliersbottle cap openerD. Match the following :1. inclined plane (a) knife2. wedge (b) grooved wheel3. screw (c) lemon squeezer4. wheel and axle (d) staircase5. pulley (e) scissors6. first class lever (f) roller skates7. second class lever (g) fishing rod8. third class lever (h) electric bulbHorizon Press130Science 'n' Us - 1 to 5
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