{"id":153968,"date":"2024-01-09T18:45:34","date_gmt":"2024-01-09T13:15:34","guid":{"rendered":"https:\/\/icsesolutions.com\/?p=153968"},"modified":"2024-01-10T10:20:30","modified_gmt":"2024-01-10T04:50:30","slug":"living-science-physics-class-6-icse-solutions-chapter-7","status":"publish","type":"post","link":"https:\/\/icsesolutions.com\/living-science-physics-class-6-icse-solutions-chapter-7\/","title":{"rendered":"Living Science Physics Class 6 ICSE Solutions Chapter 7 Simple Machine"},"content":{"rendered":"
Check Your Progress (Page 78)<\/span><\/p>\n Answer the following.<\/p>\n Question 1. Question 2. Question 3. Question 4. Question 5. A. Tick the most appropriate answer.<\/span><\/p>\n Question 1. Question 2. Question 3. Question 4. Question 5. Question 6. Question 7. Question 8. B. State if the following statements are true or false. Correct the statement if it is false.<\/span><\/p>\n Question 1. Question 2. Question 3. Question 4. Question 5. Question 6. Question 7. Question 8. C. Answer the following in a word or two or in a sentence.<\/span><\/p>\n Question 1. Question 2. Question 3. Question 4. Question 5. Question 6. D. Answer the following in short.<\/span><\/p>\n Question 1. Question 2. Question 3. Question 4. Question 5. Question 6. E. Answer the following in detail.<\/span><\/p>\n Question 1. Question 2. Single fixed pulley:<\/p>\n Single movable pulley :<\/p>\n Question 3. Question 4. Question 5. Example : If a heavy box needs to be loaded on a lony, it is far easier to push it over an inclined plane than to lift it up. Steeper the inclined plane, greater will be the effort required to push up the load. Sloping ramps, flyovers, roads on hills and staircases are all examples of inclined planes.<\/p>\n F. Give reasons for the following.<\/span><\/p>\n Question 1. Question 2. Question 3. G. Solve the following numerical problems.<\/span><\/p>\n Question 1. Question 2. Question 3. Question 4. H. Draw diagrams of the following.<\/span><\/p>\n Question 1. Question 2. Question 3. I. Solve the crossword puzzle.<\/span><\/p>\n Across
\nWhat is a machine ?
\nAnswer;
\nTools and objects that help us to perform the same amount of work with much less effort than if we did the work manually, are called machines. Example : lever, hammer, knife, etc.<\/p>\n
\nWhat do you understand by a complex machine ?
\nAnswer:
\nMachines such as sewing machines or cars that have more than one moving part are called complex machines.<\/p>\n
\nName the simplest of all types of machines.
\nAnswer:
\nLever<\/p>\n
\nState the principle of levers.
\nAnswer:
\nThe principle of a lever states that the product of the load and the load arm is always equal to the product of the effort and the effort arm.
\nLoad x Load arm = Effort x Effort arm
\n
\nThe above ratio is called the mechanical advantage of a lever.<\/p>\n
\nWhat is a Class I lever ?
\nAnswer:
\nIn Class I levers (also called levers of first order), the fulcrum lies between the load and the effort, i.e., the load and the effort are on the opposite sides of the fulcrum. Examples : See-saw, pairs of scissors, pliers, beam balance, etc.
\nThe mechanical advantage of a Class I lever is always greater than one. These levers act as force multipliers.
\n<\/p>\n
\nThe force applied on a machine to do work is called the
\na. load
\nb. effort
\nc. efficiency
\nd. fulcrum
\nAnswer:
\nb. effort<\/p>\n
\nIf the effort lies between the fulcrum and the load, then the lever belongs to which class ?
\na. Class I
\nb. Class II
\nc. Class III
\nd. Class IV
\nAnswer:
\nc. Class III<\/p>\n
\nWhich of the following is a Class II lever ?
\na. Pliers
\nb. A beam balance
\nc. A nut-cracker
\nd. A knife
\nAnswer:
\nc. A nut-cracker<\/p>\n
\nA pair of scissors is an example of a\/an
\na. wedge
\nb. lever
\nc. inclined plane
\nd. screw
\nAnswer:
\nb. lever<\/p>\n
\nThe mechanical advantage of an inclined plane is always
\na. greater than 1
\nb. less than 1
\nc. equal to 1
\nd. zero
\nAnswer:
\na. greater than 1<\/p>\n
\nThe effort required to lift a load of 800 N by using a lever having a mechanical advantage of 1.6 is
\na. 1080 N
\nb. 240 N
\nc. 720 N
\nd. 500 N
\nAnswer:
\nd. 500 N<\/p>\n
\nA machine made up of two or more sloping surface is known as .a
\na. wedge
\nb. screw
\nc. pulley
\nd. lever
\nAnswer:
\na. wedge<\/p>\n
\nThe useful work done by a machine is known as the
\na. input energy
\nb. output energy
\nc. efficiency
\nd. effort
\nAnswer:
\nb. output energy<\/p>\n
\nThere are four types of simple machines.
\nAnswer:
\nFalse. There are six types of simple machines.<\/p>\n
\nThe load and effort can act at a single point in a lever.
\nAnswer:
\nFalse. The load and effort cannot act at a single point in a lever.<\/p>\n
\nA screw is a special case of an inclined plane.
\nAnswer:
\nTrue<\/p>\n
\nThe effort required to insert a screw into wood is less than that needed to insert a nail into wood.
\nAnswer:
\nTrue<\/p>\n
\nA single movable pulley is a pulley that has its axis of rotation fixed.
\nAnswer:
\nFalse. A single fixed pulley is a pulley that has its axis of rotation fixed.<\/p>\n
\nA rotation spindle tap is an example of a wheel-and-axle arrangement.
\nAnswer:
\nTrue<\/p>\n
\nA sewing needle is a wedge type simple machine.
\nAnswer:
\nTrue<\/p>\n
\nWork done by a machine is always more than the work done on a machine.
\nAnswer:
\nFalse. Work done by a machine is always less than the work done on a machine.<\/p>\n
\nGiven an example of a Class I lever. >
\nAnswer:
\nSee-saw, pair of scissors<\/p>\n
\nWhich type of machine is used to squeeze a lemon ?
\nAnswer:
\nClass II lever<\/p>\n
\nWrite the relationship between mechanical advantage, load and effort.
\nAnswer:
\nMechanical advantage (MA) = <\/p>\n
\nName the type of machine made by putting two inclined planes together.
\nAnswer:
\nWedge .<\/p>\n
\nGive one example of a machine used to multiply speed.
\nAnswer:
\nClass III lever (hockey stick, forceps)<\/p>\n
\nWrite the formula for calculating the efficiency of a machine.
\nAnswer:
\nEfficiency =
\nThe percentage value of efficiency of a machine is calculated as :
\nEfficiency = <\/p>\n
\nExplain the various functions that a machine can perform.
\nAnswer:
\nVarious functions that a machine can perform are :<\/p>\n\n
\nWhat is the basis of classification of levers ?
\nAnswer:
\nLevers are classified on the basis of the relative positions of load, effort and fulcrum.<\/p>\n
\nWhat is the function of a screw ? Give any one use of a screw.
\nAnswer:
\nA screw is a special type of an inclined plane which has a sharp and pointed tip and can be turned (using a screw driver, bolt or a jack.) It acts as a force multiplier and less effort is required to do the work. Example : Screw forced and rotated into wood travels a greater distance with less effort than a nail would. Bolt rotating inside the fixed nut and jack used to lift a car use the principle of screw.<\/p>\n
\nUsing a suitable example, describe how a machine acts as a force multiplier.
\nAnswer:
\nIt is very difficult to open the sealed metal cap of a cold drink bottle with our bare hands. A simple machine like a bottle opener (Class II lever) multiplies the applied force and much less effort is required to open the cap. Hence, it acts as a force multiplier.<\/p>\n
\nWhat do you understand by the term \u2018efficiency of a machine\u2019?
\nAnswer:
\nThe ratio of the work done by the machine to the work done on the machine is called efficiency of a machine
\nEfficiency =
\n[Work done by a machine is called the output energy and the work done on a machine is called the input energy.]<\/p>\n
\nMention any two methods by which we can take care of machines.
\nAnswer:
\nTaking care of machines : Some of the ways in which machines should be cared for are given below.<\/p>\n\n
\nDraw simplified diagrams by clearly showing the position of load, effort and fulcrum for Class I, Class II and Class III levers.
\nAnswer:
\nClass I –
\n
\nClass II lever –
\n
\nClass III lever –
\n<\/p>\n
\nHow does a pulley make work simpler ? Differentiate between a single fixed pulley and a single movable pulley.
\nAnswer:
\nA pulley is a wheel or a circular disc that can rotate freely about its axle. It is used to lift Heavy objects. It is neither a force multiplier nor a speed multiplier. It only changes the direction of the applied force from upwards against gravity to downwards towards gravity. There are two types of pulley systems – Single fixed pulley and single movable pulley.<\/p>\n\n
\n<\/li>\n<\/ul>\n\n
\n<\/li>\n<\/ul>\n
\nExplain the wheel-and-axle arrangement in brief. How does the handle of a bicycle work for this arrangement?
\nAnswer:
\nWheel-and-axle arrangement consists of two cylinders of different diameters joined together such that if one is made to rotate, the other also rotates. The axle is a cylinderical rod fixed to the centre of a circular disc-like object called the wheel. This machine acts as a speed multiplier device. In riding a bicycle, when we apply force on the wheel (by pedal), the fixed axle rotates with it easily. This force that turns the axle produces a much larger movement of the wheel.
\n<\/p>\n
\nWhat is a wedge ? Explain the principle on which it works by giving suitable examples.
\nAnswer:
\nA wedge is a double inclined plane such that the two sloping surfaces taper to form either a sharp edge or a pointed edge. Examples : A knife, an axe, a chisel. In some special cases, the number of inclined planes used can be more than two as well. In such cases, the sloping surfaces generally taper to form either a very sharp or a pointed edge to split or pierce materials. Pins, nails and needles are examples of pointed wedges. The front end of a boat is shaped like a wedge so that it can easily cut across the flowing water. The wedge works on a principle of an inclined plane.<\/p>\n
\nWhat is an inclined plane ? What is the use of an inclined plane ?
\nAnswer:
\nAn inclined plane is a rigid sloping surface over which heavy loads can be raised or lowered to a certain height or depth. The mechanical advantae of an inclined plane is the ratio of the length of the plank to the vertical height of the load raised. Its value is greater than one. Therefore, an inclined plane acts as a force multiplier. Thus, it can be used to lift heavy loads.<\/p>\n
\nMachines arc able to make our work convenient.
\nAnswer:
\nMachines help us to perform the same amount of work with much less effort than if we did the work manually. They also make our work faster and easier by multiplying the speed or the force applied.<\/p>\n
\nThe efficiency of a machine is always less than 100%.
\nAnswer:
\nEfficiency of a machine is always less than 100% as output energy is always less than the input energy, because some energy is lost to overcome friction.<\/p>\n
\nThe front end of a boat is shaped like a wedge.
\nAnswer:
\nThe front end of a boat is shaped like a wedge so that it can easily cut across the flowing water.<\/p>\n
\nThe length of a lever is 2 m. Calculate its mechanical advantage if the fulcrum is situated at a distance of 40 cm from the effort.
\nAnswer:
\nLength of the lever = 2m = 200 cm
\nLength of the effort arm = 40 cm
\nLength of the load arm = 200 cm – 40 cm = 160 cm
\nMechanical advantage = ?
\nWe know that,
\nMechanical advantage =\u00a0
\nMA = \\(\\frac{40 \\mathrm{~cm}}{160 \\mathrm{~cm}}\\) = 0.25<\/p>\n
\nThe length of the load arm of a lever is 6 m long and the effort arm is 3 m long. What is the effort required to lift a load of 40 N ?
\nAnswer:
\nLength of the load arm = 6 m
\nLength of the effort arm = 3 m
\nLoad = 40N
\nEffort = ?
\nWe know that .
\n
\nBy putting values, we get
\n<\/p>\n
\nCalculate the mechanical advantage of a crowbar of length 240 cm if its fulcrum is situated at a distance of 40 cm from the load.
\nAnswer:
\nLength of crowbar = 240 cm
\nLength of load arm = 40 cm
\nLength of effort arm = 240 cm – 40 cm = 200 cm
\nMechanical Advantage =
\n\\(\\frac{200 \\mathrm{~cm}}{40 \\mathrm{~cm}}\\) = 5<\/p>\n
\nWhat effort will be required to lift a load of 500 N by a single movable pulley ? [Hint : Mechanical advantage of a single movable pulley is two],
\nAnswer:
\nLoad = 500 N
\nMechanical advantage (MA) = 2
\nof a single movable pulley
\nEffort = ?
\nWe know that,
\nMA =
\n\u21d2 Effort = \\(\\)\\frac{500}{2}latex] N = 250 N<\/p>\n
\nA class II lever
\nAnswer:
\nClass II lever –
\n<\/p>\n
\nA screw
\nAnswer:
\n
\nA screw<\/p>\n
\nA single movable pulley Ans.
\nAnswer:
\n<\/p>\n
\n5. The fixed point about which a lever can rotate
\n6. A type of simple machine made up of an iron bar
\n7. A type of machine formed when two inclined planes are put together
\nDown
\n1. A circular disc that can rotate freely about its axle
\n2. The force applied on a lever
\n3. A type of machine made up of a cylinderical rod with spiral threads.
\n4. The cylinderical rod fixed to the centre of a wheel
\nAnswer:
\n<\/p>\n