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Question 7 Question 4 A machine can have mechanical advantage greater than its velocity ratio. Due to friction, mechanical advantage of a machine increases. Exercise 3A — Multiple Choice Type A single fixed Pulley used to lift a bucket of water from a well. Output energy = Input energy Which of the following relations is wrong? Question 2 Efficiency = Work input / Work output Answer For an ideal machine: Answer Answer Which of the following is not an example of a machine used as a force multiplier?
Physics- chapter Machines
Question 6 The lever for which mechanical advantage is less than 1 has: Answer Question 5 Answer Answer Greater than 1 Question 1 Question 3 Which of the following statements is incorrect? Answer If the effort needed is less than the load, then mechanical advantage of the machine is: Select the incorrect statement:
(b) State the principle of an ideal machine.
M.A. > 1
Class I lever Exercise 3A — Very Short Questions Question 1 (a) What do you understand by a simple machine? Question 10 Answer Question 8 Reason — In class II or Class III levers, effort and load are on the same side of fulcrum. Answer (a) A machine is a device by which we can either overcome a large resistive force (or load) at some point by applying a small force (or effort) at a convenient point and in a desired direction or by which we can obtain a gain in speed. Answer Class II levers are designed to have: The Lever shown in the figure is: Answer Answer Effort between fulcrum and load. Class II or Class III Lever Which class of levers have effort and load on the same side of fulcrum Question 9
(ii) a practical machine? How is mechanical advantage related to the velocity ratio for (i) For an ideal machine (free from friction etc.), work output is equal to the work input, so the efficiency is equal to 1 ( or 100% ) and the mechanical advantage is numerically equal to the velocity ratio. So, (ii) speed multiplier. (i) force multiplier, For an ideal machine, M.A. = V.R. (ii) In the case of a practical machine, the mechanical advantage is always less than its velocity ratio or the output work is always less than the input work as some of the input energy is lost due to the force of friction etc. So, For a practical machine, M.A. < V.R. Question 4 (i) an ideal machine, Answer Question 3 (d) In order to obtain gain in speed — A knife. The blade of a knife moves longer by a small displacement of its handle. A machine works as a In each case state whether the velocity ratio is more than or less than 1.
(ii) When a machine works as a speed multiplier then the displacement of load is more than displacement of effort. Hence, the velocity ratio is less than 1. The efficiency of such a machine is always less than 1 as some part of input energy is lost against the force of friction. Question 6 Question 5 Answer (i) When a machine works as a force multiplier then the displacement of the load is less than the displacement of effort. Hence, the velocity ratio is more than 1. M.A. Answer Write down a relation expressing the mechanical advantage of a lever. How is mechanical advantage related with velocity ratio for an actual machine? State whether the efficiency of such a machine is equal to 1, less than 1 or more than 1. For an actual machine, the mechanical advantage is always less than its velocity ratio or the output work is always less than the input work. The expression of the mechanical advantage of a lever is: Answer In each case state whether the velocity ratio is more than or less than 1.
(f) sugar tongs — Class III What type of lever is formed by a human body while (b) a catapult (c) Claw hammer — Class I (b) A catapult — Class I (d) a wheel barrow (d) A wheel barrow — Class II (a) A door — Class II (f) sugar tongs Answer (c) claw hammer Question 9 (e) A fishing rod — Class III (e) a fishing rod (b) raising the weight of body on toes? (a) raising a load on the palm, and
(a) When a human body raises a load on the palm then it is an example of a Class III lever. The elbow joint acts as fulcrum F at one end, biceps exerts the effort in the middle and load L on the palm is at the other end. What type of lever is formed by the human body while. Machines, Concise Physics Solutions ICSE Class 10. Give an example of each class of lever in a human body. (b) When raising the weight of body on toes then it is a Class II lever. The fulcrum F is at toes at one end, the load L (i.e. weight of the body) is in the middle and the effort E by muscles is at the other end. Answer (ii) The action of raising the weight of the body on toes is an example of Class II lever. In this case, the fulcrum F is at toes at one end, the load L (i.e. the weight of the body) is in the middle and effort E by muscles is at the other end. The action of nodding of the head is a Class I lever. In this case the spine acts as the fulcrum F, load L is at its front part while effort E is at its rear part. Machines, Concise Physics Solutions ICSE Class 10. (i) The action of nodding of the head is a Class I lever. In this case the spine acts as the fulcrum F, load L is at its front part while effort E is at its rear part. Answer What type of lever is formed by the human body while. Machines, Concise Physics Solutions ICSE Class 10. The examples of each class of lever in a human body are: Question 10
Question 3 Answer A jack is a mechanical lifting device used to lift heavy loads. Answer What is the purpose of a jack in lifting a car by it? (c) Changing the direction of effort to a convenient direction. Question 2 A jack works as a force multiplier, as with a little effort on the jack we are able to lift heavy load like a car. It acts as a force multiplier. Machines are useful to us in — State four ways in which machines are useful to us. Answer (b) Lifting a heavy load by applying a less effort. What do you understand by an ideal machine? How does it differ from a practical machine? An ideal machine is that where there is no loss of energy i.e. the work output is (a) Changing the point of application of effort to a convenient point. (d) For obtaining a gain in speed.
Explain the term mechanical advantage. State its unit. Mechanical Advantage= Answer As mechanical advantage is a ratio of similar quantities so it has no unit.
Mechanical Advantage Define the term velocity ratio. State its unit. The ratio of the load to the effort is called mechanical advantage of the machine. Question 5 Load In a practical machine output energy is always less than the input energy i.e. there is some loss of energy during the operation which is not the case in an ideal machine. Effort Question 4 Effort An ideal machine is that where there is no loss of energy i.e. the work output is equal to the work input. An ideal machine is 100% efficient. Answer Load
Work output It has no unit as it is the ratio of two similar quantities. Can a machine act as a force multiplier and speed multiplier simultaneously? When does a machine act as (b) a speed multiplier. (a) a force multiplier (b) A machine acts as a speed multiplier when the effort arm is shorter than the Due to the above reasons, the velocity ratio of the machine does not change but it's mechanical advantage decreases so its efficiency decreases. A machine is not always 100% efficient due to — Work Input Answer (a) A machine acts as a force multiplier when the effort arm is longer than the load arm. The mechanical advantage in such cases is greater than 1. Question 7 (a) friction (b) weight of moving parts of machine of a given design.
Answer (b) The term that does not change for a machine of a given design is its velocity ratio. Answer No, it is not possible for a machine to act as a force multiplier and speed multiplier simultaneously. (b) A machine acts as a speed multiplier when the effort arm is shorter than the load arm. The mechanical advantage in such cases is less than 1. State one reason why mechanical advantage is less than the velocity ratio for an actual machine. (a) State the relationship between mechanical advantage, velocity ratio and efficiency. M.A. = V.R. x η (a) The mechanical advantage of a machine is equal to the product of its efficiency and velocity ratio. Question 8 (b) Name the term that will not change for a machine of a given design. Question 9 For a machine used as a force multiplier, effort < load while for a machine used to obtain a gain in speed, effort > load. Hence, it is not possible for a single machine to act as both, simultaneously.
Example — sugar tongs, foot treadle. (iii) Class III levers — In these type of levers, the fulcrum F and the load L are at the two ends of the lever and the effort E is somewhere in between the fulcrum F and the load L. Both a pair of scissors and a pair of pliers belong to the same class of levers. Name the class of lever. Which one has the mechanical advantage less than 1? As the blades of the scissors are longer than its handles, so the effort arm is shorter than the load arm. Hence, the mechanical advantage of a pair of scissors is less than 1. Figure shows a lemon crusher. In the diagram, mark the position of the directions of load L and effort E. Name the class of lever. Machines, Concise Physics Class 10 Solutions. Question 13 (ii) Class II levers — In these type of levers, the fulcrum F and the effort E are at the two ends of the lever and the load L is somewhere in between the effort E and the fulcrum F. Question 12 Figure shows a lemon crusher. Example — a nutcracker, a bottle opener. Answer A pair of scissors and a pair of pliers both belong to class I lever.
Lemon crusher with position of the directions of load L and effort E labelled. Machines, Concise Physics Class 10 Solutions. The diagram below shows a rod lifting a stone. The diagram below shows a rod lifting a stone. Mark position of fulcrum F and draw arrows to show the directions of load L and effort E. What class of lever is the rod? Machines, Concise Physics Class 10 Solutions. (a) Labelled diagram of lemon crusher is shown below: of load L and effort E. Name the class of lever. Machines, Concise Physics Class 10 Solutions. (c) Give one more example of the same class of lever stated in part (b). (a) Mark position of fulcrum F and draw arrows to show the directions of load L and effort E. (b) Name the class of lever. Answer (b) It is a class II lever. (a) Below diagram shows the position of fulcrum F and the directions of load L and effort E Question 14 (a) In the diagram, mark the position of the fulcrum F and the line of action of load L and effort E. Answer (b) What class of lever is the rod?
and the effort arm is always smaller than the load arm. Therefore, the mechanical advantage of class III lever is always less than 1. (a) A bottle opener is an example of Class II lever, as the fulcrum F and the effort E are at the two ends of the lever and the load is in between the fulcrum F and the effort E. Class III levers have mechanical advantage less than 1 so as effort arm is always less than the load arm, so we do not get gain in force, but we get gain in speed, i.e. a larger displacement of load is obtained by a smaller displacement of effort. (a) a bottle opener, and State the class of levers and the relative positions of load L, effort E) and fulcrum F) in a bottle opener, and sugar tongs. Machines, Concise Physics Class 10 Solutions. Classes III levers have mechanical advantage less than 1. Why are they then used? (b) sugar tongs. Answer Answer Question 17 (b) Sugar tongs is an example of Class III lever, as the fulcrum F and the load L are at the two ends of the lever and the effort E is in between the fulcrum F and Question 18 State the class of levers and the relative positions of load L, effort E) and fulcrum F) in
It is a Class III lever. Question 1 Answer Positions of load L, effort E and fulcrum F in the forearm are labelled in the diagram. Machines, Concise Physics Class 10 Solutions. Suppose a machine overcomes a load L by the application of effort E. Indicate the positions of load L, effort E and fulcrum F in the forearm shown below. Name the class of lever. Let, the displacement of effort = dE and Answer Derive a relationship between mechanical advantage, velocity ratio and efficiency of a machine. (b) Sugar tongs is an example of Class III lever, as the fulcrum F and the load L are at the two ends of the lever and the effort E is in between the fulcrum F and the load L. Exercise 3A — Long Questions Question 19 The positions of load L, effort E and fulcrum F in the forearm are shown below: Indicate the positions of load L, effort E and fulcrum F in the forearm shown. Machines, Concise Physics Class 10 Solutions.
