Goyal Brothers Textbook Solutions: Machines

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Machines 
 
Exercise – 1 
Question 1. 
(a) What is a machine ? 
(b) State three functions of machine. 
Answer: 
(a) Machine : “Is a device which is used to transmit force to change the direction of 
force or to obtain speed.” 
(b) Functions of machines : 
1. To act as force multiplier 
2. To shift the point of application to a convenient place. 
3. To multiply speed. 
4. To change the direction of the force applied for greater ease and comfort. 
Question 2. 
(a) Name six simple machines. 
(b) Give one practical example of each machine named in (a) 
Answer: 
(a) Simple machines are : 
1. Lever 
2. Pulley 
3. Wedge 
4. Inclined plane 
5. Wheel and axle 
6. Screw 
(b) Example of : 
1. Liver : is handle of common water pump helps in multiplying effort 
2. Pulley : gears, used for changing the direction of the effort 
3. Wedge : axe, A knife are the examples. 
4. Inclined plane : Ramp or staircase or screw jack. 
5. Wheel and axle : Free wheel or crank wheel of bicycle. 
6. Screw : Screw bolt. 
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Machines 
 
Exercise – 1 
Question 1. 
(a) What is a machine ? 
(b) State three functions of machine. 
Answer: 
(a) Machine : “Is a device which is used to transmit force to change the direction of 
force or to obtain speed.” 
(b) Functions of machines : 
1. To act as force multiplier 
2. To shift the point of application to a convenient place. 
3. To multiply speed. 
4. To change the direction of the force applied for greater ease and comfort. 
Question 2. 
(a) Name six simple machines. 
(b) Give one practical example of each machine named in (a) 
Answer: 
(a) Simple machines are : 
1. Lever 
2. Pulley 
3. Wedge 
4. Inclined plane 
5. Wheel and axle 
6. Screw 
(b) Example of : 
1. Liver : is handle of common water pump helps in multiplying effort 
2. Pulley : gears, used for changing the direction of the effort 
3. Wedge : axe, A knife are the examples. 
4. Inclined plane : Ramp or staircase or screw jack. 
5. Wheel and axle : Free wheel or crank wheel of bicycle. 
6. Screw : Screw bolt. 
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Question 3. 
Define the following terms with reference to a machine 
(a) Total load 
(b) useful load 
(c) effort 
(d) ideal machine 
(e) ideal mechanical advantage 
(f) actual mechanical advantage 
(g) velocity ratio 
(h) efficiency 
Answer: 
(a) Total load : Load lifted by machine + resistance over come. 
(b) Useful load : “The load, a machine in able to lift.” 
(c) Effort : The effort applied by us on the machine. 
(d) Ideal machine : A machine whose parts are weightless and frictionless such that 
what so ever is the energy spent on it same is the energy produced by it, is called a 
perfect machine.” 
(e) Ideal mechanical advantage : “The ratio between total load moved (or resistance 
overcome) to the effort applied is called ideal mechanical advantage.” 
(f) Actual mechanical advantage : “The ratio between useful load moved to the effort 
applied is called actual mechanical advantage”. 
(g) Velocity ratio : [V.R.] : “Is the ratio of velocity of effort to velocity of load.” 
i. e “Ratio of effort arm to load arm.” 
(h) Efficiency : (?) “Efficiency of a machine is the ratio of useful work done by machine 
to the work put into the machine by the effort.” 
Question 4. 
Prove that efficiency of a machine is the ratio between mechanical advantage and 
velocity ratio. 
Answer: 
Relation Between M.A., V.R And Efficiency : 
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Machines 
 
Exercise – 1 
Question 1. 
(a) What is a machine ? 
(b) State three functions of machine. 
Answer: 
(a) Machine : “Is a device which is used to transmit force to change the direction of 
force or to obtain speed.” 
(b) Functions of machines : 
1. To act as force multiplier 
2. To shift the point of application to a convenient place. 
3. To multiply speed. 
4. To change the direction of the force applied for greater ease and comfort. 
Question 2. 
(a) Name six simple machines. 
(b) Give one practical example of each machine named in (a) 
Answer: 
(a) Simple machines are : 
1. Lever 
2. Pulley 
3. Wedge 
4. Inclined plane 
5. Wheel and axle 
6. Screw 
(b) Example of : 
1. Liver : is handle of common water pump helps in multiplying effort 
2. Pulley : gears, used for changing the direction of the effort 
3. Wedge : axe, A knife are the examples. 
4. Inclined plane : Ramp or staircase or screw jack. 
5. Wheel and axle : Free wheel or crank wheel of bicycle. 
6. Screw : Screw bolt. 
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Question 3. 
Define the following terms with reference to a machine 
(a) Total load 
(b) useful load 
(c) effort 
(d) ideal machine 
(e) ideal mechanical advantage 
(f) actual mechanical advantage 
(g) velocity ratio 
(h) efficiency 
Answer: 
(a) Total load : Load lifted by machine + resistance over come. 
(b) Useful load : “The load, a machine in able to lift.” 
(c) Effort : The effort applied by us on the machine. 
(d) Ideal machine : A machine whose parts are weightless and frictionless such that 
what so ever is the energy spent on it same is the energy produced by it, is called a 
perfect machine.” 
(e) Ideal mechanical advantage : “The ratio between total load moved (or resistance 
overcome) to the effort applied is called ideal mechanical advantage.” 
(f) Actual mechanical advantage : “The ratio between useful load moved to the effort 
applied is called actual mechanical advantage”. 
(g) Velocity ratio : [V.R.] : “Is the ratio of velocity of effort to velocity of load.” 
i. e “Ratio of effort arm to load arm.” 
(h) Efficiency : (?) “Efficiency of a machine is the ratio of useful work done by machine 
to the work put into the machine by the effort.” 
Question 4. 
Prove that efficiency of a machine is the ratio between mechanical advantage and 
velocity ratio. 
Answer: 
Relation Between M.A., V.R And Efficiency : 
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Question 5. 
Give two reasons, why machine cannot be 100% efficient. 
Answer: 
1. Apart of input is always used in moving the parts of machine. 
2. A part of input is wasted in overcoming friction between various parts of machine. 
Question 6. 
(a) Define lever. What are its kinds ? 
(b) How will you determine the order of a lever ? 
Answer: 
(a) Lever : “Is a straight or bent rigid rod which can turn about a fixed point called 
fulcrum” 
(b) Out of effort (E), Load (L) and Fulcrum (F), the one which is in between the other two 
determines the order of lever i.e. 
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Machines 
 
Exercise – 1 
Question 1. 
(a) What is a machine ? 
(b) State three functions of machine. 
Answer: 
(a) Machine : “Is a device which is used to transmit force to change the direction of 
force or to obtain speed.” 
(b) Functions of machines : 
1. To act as force multiplier 
2. To shift the point of application to a convenient place. 
3. To multiply speed. 
4. To change the direction of the force applied for greater ease and comfort. 
Question 2. 
(a) Name six simple machines. 
(b) Give one practical example of each machine named in (a) 
Answer: 
(a) Simple machines are : 
1. Lever 
2. Pulley 
3. Wedge 
4. Inclined plane 
5. Wheel and axle 
6. Screw 
(b) Example of : 
1. Liver : is handle of common water pump helps in multiplying effort 
2. Pulley : gears, used for changing the direction of the effort 
3. Wedge : axe, A knife are the examples. 
4. Inclined plane : Ramp or staircase or screw jack. 
5. Wheel and axle : Free wheel or crank wheel of bicycle. 
6. Screw : Screw bolt. 
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Question 3. 
Define the following terms with reference to a machine 
(a) Total load 
(b) useful load 
(c) effort 
(d) ideal machine 
(e) ideal mechanical advantage 
(f) actual mechanical advantage 
(g) velocity ratio 
(h) efficiency 
Answer: 
(a) Total load : Load lifted by machine + resistance over come. 
(b) Useful load : “The load, a machine in able to lift.” 
(c) Effort : The effort applied by us on the machine. 
(d) Ideal machine : A machine whose parts are weightless and frictionless such that 
what so ever is the energy spent on it same is the energy produced by it, is called a 
perfect machine.” 
(e) Ideal mechanical advantage : “The ratio between total load moved (or resistance 
overcome) to the effort applied is called ideal mechanical advantage.” 
(f) Actual mechanical advantage : “The ratio between useful load moved to the effort 
applied is called actual mechanical advantage”. 
(g) Velocity ratio : [V.R.] : “Is the ratio of velocity of effort to velocity of load.” 
i. e “Ratio of effort arm to load arm.” 
(h) Efficiency : (?) “Efficiency of a machine is the ratio of useful work done by machine 
to the work put into the machine by the effort.” 
Question 4. 
Prove that efficiency of a machine is the ratio between mechanical advantage and 
velocity ratio. 
Answer: 
Relation Between M.A., V.R And Efficiency : 
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Question 5. 
Give two reasons, why machine cannot be 100% efficient. 
Answer: 
1. Apart of input is always used in moving the parts of machine. 
2. A part of input is wasted in overcoming friction between various parts of machine. 
Question 6. 
(a) Define lever. What are its kinds ? 
(b) How will you determine the order of a lever ? 
Answer: 
(a) Lever : “Is a straight or bent rigid rod which can turn about a fixed point called 
fulcrum” 
(b) Out of effort (E), Load (L) and Fulcrum (F), the one which is in between the other two 
determines the order of lever i.e. 
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If F is in between L and E, then it is lever of 1 st order 
If L is in between F and E. It is of second order lever. 
If E is in between L and F, it is Illrd order lever. 
Question 7. 
To which order do the following levers belong and why ? 
(a) A railway signal 
(b) A man cutting bread with a knife 
(c) A boy writing a piece of paper 
(d) A nut cracker 
(e) handle of a water pump 
(f) see-saw 
(g) forceps 
(h) A man rowing a boat 
(i) A lock and key 
(j) Soda water opener 
(k) a door 
(l) motorcarfoot brake 
(m) fishing rod 
(n) lemon squeezer. 
Answer: 
(a) A railway signals – Lever of 1st order as F is in between load and effort 
(b) Cutting a bread with knife is third order lever as effort is in between load and 
fulcrum. 
 
(c) A boy writing a piece of paper is Illrd order lever as effort is in between load and 
fulcrum. 
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Machines 
 
Exercise – 1 
Question 1. 
(a) What is a machine ? 
(b) State three functions of machine. 
Answer: 
(a) Machine : “Is a device which is used to transmit force to change the direction of 
force or to obtain speed.” 
(b) Functions of machines : 
1. To act as force multiplier 
2. To shift the point of application to a convenient place. 
3. To multiply speed. 
4. To change the direction of the force applied for greater ease and comfort. 
Question 2. 
(a) Name six simple machines. 
(b) Give one practical example of each machine named in (a) 
Answer: 
(a) Simple machines are : 
1. Lever 
2. Pulley 
3. Wedge 
4. Inclined plane 
5. Wheel and axle 
6. Screw 
(b) Example of : 
1. Liver : is handle of common water pump helps in multiplying effort 
2. Pulley : gears, used for changing the direction of the effort 
3. Wedge : axe, A knife are the examples. 
4. Inclined plane : Ramp or staircase or screw jack. 
5. Wheel and axle : Free wheel or crank wheel of bicycle. 
6. Screw : Screw bolt. 
Downloaded from https://www.ncertbooksolutions.com/
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Question 3. 
Define the following terms with reference to a machine 
(a) Total load 
(b) useful load 
(c) effort 
(d) ideal machine 
(e) ideal mechanical advantage 
(f) actual mechanical advantage 
(g) velocity ratio 
(h) efficiency 
Answer: 
(a) Total load : Load lifted by machine + resistance over come. 
(b) Useful load : “The load, a machine in able to lift.” 
(c) Effort : The effort applied by us on the machine. 
(d) Ideal machine : A machine whose parts are weightless and frictionless such that 
what so ever is the energy spent on it same is the energy produced by it, is called a 
perfect machine.” 
(e) Ideal mechanical advantage : “The ratio between total load moved (or resistance 
overcome) to the effort applied is called ideal mechanical advantage.” 
(f) Actual mechanical advantage : “The ratio between useful load moved to the effort 
applied is called actual mechanical advantage”. 
(g) Velocity ratio : [V.R.] : “Is the ratio of velocity of effort to velocity of load.” 
i. e “Ratio of effort arm to load arm.” 
(h) Efficiency : (?) “Efficiency of a machine is the ratio of useful work done by machine 
to the work put into the machine by the effort.” 
Question 4. 
Prove that efficiency of a machine is the ratio between mechanical advantage and 
velocity ratio. 
Answer: 
Relation Between M.A., V.R And Efficiency : 
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Question 5. 
Give two reasons, why machine cannot be 100% efficient. 
Answer: 
1. Apart of input is always used in moving the parts of machine. 
2. A part of input is wasted in overcoming friction between various parts of machine. 
Question 6. 
(a) Define lever. What are its kinds ? 
(b) How will you determine the order of a lever ? 
Answer: 
(a) Lever : “Is a straight or bent rigid rod which can turn about a fixed point called 
fulcrum” 
(b) Out of effort (E), Load (L) and Fulcrum (F), the one which is in between the other two 
determines the order of lever i.e. 
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If F is in between L and E, then it is lever of 1 st order 
If L is in between F and E. It is of second order lever. 
If E is in between L and F, it is Illrd order lever. 
Question 7. 
To which order do the following levers belong and why ? 
(a) A railway signal 
(b) A man cutting bread with a knife 
(c) A boy writing a piece of paper 
(d) A nut cracker 
(e) handle of a water pump 
(f) see-saw 
(g) forceps 
(h) A man rowing a boat 
(i) A lock and key 
(j) Soda water opener 
(k) a door 
(l) motorcarfoot brake 
(m) fishing rod 
(n) lemon squeezer. 
Answer: 
(a) A railway signals – Lever of 1st order as F is in between load and effort 
(b) Cutting a bread with knife is third order lever as effort is in between load and 
fulcrum. 
 
(c) A boy writing a piece of paper is Illrd order lever as effort is in between load and 
fulcrum. 
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(d) A nut cracker is II nd order lever as load is in between effort and fulcrum. 
 
(e) Handle of water pump : 1st order lever as fulcrum is in between effort and load 
 
(f) See-saw : Lever of 1st order as fulcrum is in between load and effort 
 
(g) Forceps : Illrd order lever as effort is in between fulcrum and load. 
 
(h) A man rowing a boat : End order of lever as load is in between effort and fulcrum 
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