Bissoy.com
Doctors Medicines MCQs Q&A

A force was applied on a door in four ways. From the given top views for the door, the representation for zero torque is:

A force was applied on a door in four ways. From the given top views for the door, the representation for zero torque is: Correct Answer <img alt="F1 Jitendra Kumar Anil 05.04.21 D7" src="//storage.googleapis.com/tb-img/production/21/04/F1_Jitendra%20Kumar_Anil_05.04.21_D7.png" style="width: 138px; height: 137px;">

The correct answer is option 1) 

CONCEPT:

  • Torque: Torque is the turning effect produced on an object due to a force acting on it at a distance from a fixed point. The object tends to turn about this fixed point.
    • It is defined mathematically as the cross product of force and the perpendicular distance to an axis of rotation.
    • Consider a fore F acting at a distance r from a fixed point O as shown.

The torque produced is given by:

τ = r × F = rFsinθ 

  • The SI unit of torque is N-m.

[ alt="F1 Jitendra Kumar Anil 05.04.21 D1" src="//storage.googleapis.com/tb-img/production/21/04/F1_Jitendra%20Kumar_Anil_05.04.21_D1.png" style="width: 349px; height: 104px;">

  • Movement of doors: Doors have a fixed axis of rotation for their movement. The hinges provided on the edges of the doors help in the turning motion. When a force is applied on the doorknob, the perpendicular distance between the hinges and the doorknob acts as the moment arm. 

[ alt="F1 Jitendra Kumar Anil 05.04.21 D6" src="//storage.googleapis.com/tb-img/production/21/04/F1_Jitendra%20Kumar_Anil_05.04.21_D6.png" style="width: 343px; height: 210px;">

EXPLANATION:

Torque = Moment arm × Force applied = r × F = rFsinθ 

Hence, the torque produced will be zero if:

  1. either moment arm or force applied is zero
  2. the angle between moment arm and force is zero.
[ alt="F1 Jitendra Kumar Anil 05.04.21 D7" src="//storage.googleapis.com/tb-img/production/21/04/F1_Jitendra%20Kumar_Anil_05.04.21_D7.png" style="width: 138px; height: 137px;">
  • Here, the force is applied at the point of rotation. So, moment arm = 0.
  • Thus torque will be zero.
[ alt="F1 Jitendra Kumar Anil 05.04.21 D8" src="//storage.googleapis.com/tb-img/production/21/04/F1_Jitendra%20Kumar_Anil_05.04.21_D8.png" style="width: 141px; height: 197px;">
  • The force applied is perpendicular and far away from the point of rotation.
  • The maximum moment arm distance causes maximum torque.
  • Torque is not zero.
[ alt="F1 Jitendra Kumar Anil 05.04.21 D9" src="//storage.googleapis.com/tb-img/production/21/04/F1_Jitendra%20Kumar_Anil_05.04.21_D9.png" style="width: 137px; height: 197px;">
  • The force applied is perpendicular and away from the point of rotation.
  • So, torque will not be zero.
[ alt="F1 Jitendra Kumar Anil 05.04.21 D10" src="//storage.googleapis.com/tb-img/production/21/04/F1_Jitendra%20Kumar_Anil_05.04.21_D10.png" style="width: 137px; height: 135px;">
  • The force applied is perpendicular and away from the point of rotation.
  • So, torque will not be zero.

Related Questions

In the given question, a part of the sentence is printed in bold. Below the sentence three alternatives to the bold part are given which may help improve the sentence. Choose the option that reflects the correct use of the phrase in the context of the sentence. In case the given sentence is correct, your answer is (E) i.e. No correction required. Historians believe that much of Jesus story can be reconstructed, without the help of Bible, and with just the views of historians who lived during his time. I. without the help of Bible, and by just the views II. without the help from Bible, and with just the views III. without the help of the Bible, and with just the views
A 10 kW, 400 V, 3-phase, 4-pole, 50 Hz induction motor develops the rated output at rated voltage with its slip rings shorted. The maximum torque is twice the full load torque occurs at the slip of 10% with zero external resistance in the rotor circuit. An external resistance is now tripled in the rotor circuit. Then the slip at which maximum torque occur for the same load torque is?
Certain facts about Force are given below. Identify the true information. A. Force is a scalar quantity. B. Gravitational force is the weakest force. C. Electromagnetic force is the strongest force. D. When sum of all forces acting on a body is zero, the body is said to be in a state of equilibrium.
In this question, the first and last sentences of the passage are numbered 1 and 6. The rest of the passage is split into four parts and named P, Q, R, and S. These four parts are not given in their proper order. Read the sentence and find out which of the four combinations is correct. S1: A force exists between everybody in the universe. P: Normally it is very small but when one of the bodies is a planet, like earth, the force is considerable. Q: It has been investigated by many scientists including Galileo and Newton. R: Everything on or near the surface of the earth is attracted by the mass of the earth. S: This gravitational force depends on the mass of the bodies involved. S6: The greater the mass, the greater is the earth's force of attraction on it. We can call this force of attraction gravity. The Proper sequence should be:
For a three phase induction motor, maximum torque is double the full load torque and starting torque is 1.6 times the full load torque. To get a full load slip of 5%, percentage reduction in the rotor resistance should be?
Directions : In each of the following questions a statement is given, followed by two conclusions. Give answer : Statements : In a highly centralised power structure, in which even senior cabinet ministers are prepared to reduce themselves to pathetic countries or yesmen airing views that are primarily intended to anticipate or reflect the Prime Minister's own performances, there can be no place for any consensus that is quite different from real or contrived unanimity of opinion, expressed through a well orchestrated endorsement of the leader's actions. Conclusions : I. The Ministers play safe by not giving anti-government views. II. The Prime Minister does not encourage his colleagues to render their own views.
Directions : In each of the following questions a statement is given, followed by two conclusions. Give answer :

Statements : In a highly centralised power structure, in which even senior cabinet ministers are prepared to reduce themselves to pathetic countries or yesmen airing views that are primarily intended to anticipate or reflect the Prime Minister's own performances, there can be no place for any consensus that is quite different from real or contrived unanimity of opinion, expressed through a well orchestrated endorsement of the leader's actions.

Conclusions :
I. The Ministers play safe by not giving anti-government views.
II. The Prime Minister does not encourage his colleagues to render their own views.
The question below consists of a set of labelled sentences. Out of the four options given, select the most logical order of the sentences to form a coherent paragraph. P: Inclusion is also about finding different ways of teaching so that classrooms actively involve all children. It also means finding ways to develop friendships, relationships and mutual respect between all children, and between children and teachers in the school. Q: Creativity may mean teachers learning to teach in different ways or designing their lessons so that all children can be involved. R: Inclusive education is about looking at the ways our schools, classrooms, programs and lessons are designed so that all children can participate and learn. S: All children are at all times ready to attend regular schools and classrooms. Their participation is not something that must be earned. Inclusive education is a way of thinking about how to be creative to make our schools a place where all children can participate.
A 10 kW, 400 V, 3-phase, 4-pole, 50 Hz induction motor develops the rated output at rated voltage with its slip rings shorted. The maximum torque equal to twice the full load torque occurs at the slip of 10% with zero external resistance in the rotor circuit. The slip at the full load torque will be?
A 10 kW, 400 V, 3-phase, 4-pole, 50 Hz induction motor develops the rated output at rated voltage with its slip rings shorted. The maximum torque is twice the full load torque occurs at the slip of 10% with zero external resistance in the rotor circuit. The speed at the full load torque will be?