# Mechanical Engineering - Engineering Mechanics - Discussion

### Discussion :: Engineering Mechanics - Section 1 (Q.No.1)

1.

According to principle of conservation of energy, the total momentum of a system of masses in any direction remains constant unless acted upon by an external force in that direction.

 [A]. True [B]. False

Explanation:

No answer description available for this question.

 Sundar said: (Nov 20, 2012) The law of conservation of energy, first formulated in the nineteenth century, is a law of physics. It states that the total amount of energy in an isolated system remains constant over time. The total energy is said to be conserved over time. For an isolated system, this law means that energy can change its location within the system, and that it can change form within the system, for instance chemical energy can become kinetic energy, but that energy can be neither created nor destroyed. From: http://en.wikipedia.org/wiki/Conservation_of_energy

 Vipul Kumar said: (Feb 2, 2013) This should be like this only, the total momentum of a system of masses in any direction remains constant unless acted upon by an external force in any (that) direction. Momentum will change if we apply force in any direction.

 Rohit said: (Apr 1, 2013) Principle of conservation of energy states that energy can neither be created nor be destroyed.

 Mayukh said: (Apr 3, 2013) The statement is newton's second law not law of conservation of energy.

 Nikhil said: (Apr 19, 2013) For the momentum we need mass and the movement of the mass so it is the phenomenon which deals with the moving mass interaction and also a continuous change which can never be constant. Because momentum = mass *ds/dt and ds/dt term is a continuous change of displacement with respect to time.

 Abhishek Chandrakar said: (May 5, 2013) According to principle of energy conservation, energy can't be created can't be destroyed. The definition not belongs to the statement.

 Raj Shah said: (May 8, 2013) The total momentum of a system of masses in any direction remains constant unless acted upon by an external force in any (that) direction. Momentum will change if we apply force in any direction.

 Velmurugan said: (May 11, 2013) Principle of conservation energy states that energy can neither be created nor destroyed.

 Bhuwan said: (May 28, 2013) There is no description of external momentum and secondly force may be applied in any direction and here only one direction is described.

 Phanindra said: (Jun 25, 2013) Principle of conservation states that energy neither be created nor destroyed but transfers from one form to another.

 Ajay Borkar said: (Jul 5, 2013) Principle of conservation of energy states that energy can neither be created nor be destroyed but can changes into another form. And remaining statement shows about the law of linear momentum.

 Harshil Prajapati said: (Jul 10, 2013) For example if we take the ball and it could apply force what is action of ball? - ball direction change and its apply to the force.

 Arbind Rai said: (Jul 10, 2013) We know that momentum is multiplication of mass & velocity and velocity never will be constant because velocity is vector quantity so momentum of any system not constant in any direction.

 Lokesh Choudhary said: (Jul 20, 2013) We know that energy can neither be created nor be destroyed but can change into another form.

 Sudhanshu Shekhar Rana said: (Jul 30, 2013) I think the correct answer will be option(A) because in order to change the momentum of any system in any dirn we will need to change the velocity which occurs only when there is net external force on the system.

 Kirankumar said: (Aug 17, 2013) The total momentum of a system of masses in any direction remains constant unless acted upon by an external force in that direction. This is right. But in our question is according to conservation of energy. Without external force concern. The body should move. Energy neither created nor destroyed.

 Bilal said: (Sep 11, 2013) The force applied should be an external 'unbalanced' force in that direction.

 Farrukh Waseem said: (Sep 26, 2013) The principle of energy says that the energy in any system can't be created and also destroyed infect one thing is possible that it changes in another form.

 Vinay said: (Oct 3, 2013) There is no description of external momentum and secondly force may be applied in any direction and here only one direction is described. But according to newton I can say it is wrong.

 Purnendra said: (Oct 12, 2013) Momentum is a vector quantity so change in direction change the momentum.

 Srikanth said: (Nov 11, 2013) Principle of conservation of energy states that energy can neither be created nor be destroyed but can be transformed from one form to another form.

 Sachendra Chaturvedi said: (Dec 1, 2013) This principle is called conservation of momentum.

 Namrata Mishra said: (Dec 25, 2013) According to law of conservation of energy charge cannot be created nor destroyed but transferred from one body to other so if two bodies collide their mass will change automatically whether or not an external forces Are applied.

 Suresh Kumawat said: (Dec 27, 2013) The statment is related to the newton's second law.

 Anant Gyan Punj said: (Dec 28, 2013) The reason is that total momentum includes linear and angular momentum, since linear momentum is conserved in that direction if external force is not acting in that direction. But angular momentum may or may not be conserved as that force may create torque. Hence total momentum will not be conserve.

 Vivek said: (Jan 23, 2014) Its not law of conversation of energy. It is a part off statement from newton's law.

 Shai said: (Feb 10, 2014) The statement is newton's first law.

 Swapnil said: (Mar 10, 2014) Newtons 2 law and law of conservation of energy combined. So it is false statement.

 Chandan said: (Mar 11, 2014) The statement is actually true. But It explains "Law of conservation of Momentum" not the Energy.

 Karakala Jalandar Reddy said: (Mar 11, 2014) Law of conservation of energy system neither be created nor be destroyed.

 Md Aftab Alam said: (Mar 17, 2014) According to principle of conservation of energy "energy cannot be created nor be destroyed but it can be transformed from one form to another". The given statement follows the Newton's 2nd law of motion which states "Rate of change of momentum(m x a) is directly proportional to the force(F) which applied in that direction".

 Paresh said: (Jun 13, 2014) According to principle of energy conservation do not destroy the energy, energy changes one phase to other phase.

 Md Mahfooz said: (Sep 15, 2014) Law of conservation of energy: Energy is neither created nor destroy but its can be change one form to another form.

 Anil Shukla said: (Oct 6, 2014) Law of conservation of energy: Energy is neither created nor destroy but its can be change one form to another form. Law of linear momentum: The total momentum of a system of masses in any direction remains constant unless acted upon by an external force in that direction. BOTH LAWS OPPOSE EACH OTHER?

 Mukesh said: (Oct 9, 2014) Free molecule have different masses & momentum so without acting force.

 Satyajit Sahu said: (Oct 14, 2014) Here, there may be variation of air resistance and road evenness for that, it would change its momentum.

 Venu\$Sai said: (Oct 21, 2014) This question states that newton's first law.

 Sunil said: (Dec 7, 2014) According to conservation of energy: Energy neither created nor destroyed but it can change one form to another.

 Nikita Jadhav said: (Mar 18, 2015) Answer B is wrong because the given question is Newton second law and not the energy conservation law.

 Saroj Sharma said: (Mar 30, 2015) It is true that energy not created nor destroyed transformation of energy from one form to another possible. So given description is wrong.

 Saket Kumar said: (Apr 14, 2015) Law of conservation of energy is first law of thermodynamics where as law of conservation of momentum is Newton's second law and both law are not similar so statement is wrong.

 Sanket Haste said: (Jun 14, 2015) Linear momentum is also a conserved quantity, meaning that if a closed system is not affected by external forces, its total linear momentum cannot change. In classical mechanics, conservation of linear momentum is implied by Newton's laws; but it also holds in special relativity (with a modified formula) and, with appropriate definitions, a (generalized) linear momentum conservation law holds in electrodynamics, quantum mechanics, quantum field theory, and general relativity.

 Devanesan Andrews said: (Jun 24, 2015) It will change by applying force in any direction.

 Shailesh said: (Jul 9, 2015) The law of conservation of energy simply tells that energy in any form can neither be created nor be destroyed. It changes from one form of energy to another form of energy.

 Vemburaj said: (Jul 30, 2015) If a body has some constant momentum in one direction, it means that a constant external force is acting on it. But if the momentum has to change in magnitude in that direction then an external unbalanced force has to act. Here only external force is given and not external unbalanced force hence answer is false.

 Divyanshu said: (Aug 18, 2015) Momentum doesn't need constant force, if a body is accelerating in a direction then there must be a constant force applied on it, also the question is asking about SYSTEM OF MASSES, of which momentum can be changed in a by applying force in any direction & not in particularly that direction.

 Krunal Patil said: (Sep 22, 2015) Momentum changes with gravity, and gravity changes from place to place.

 Chandra Deep said: (Oct 8, 2015) It's all about law of conservation of energy.

 Rahul Thakur said: (Oct 10, 2015) Principle of conservation of energy states that energy can neither be created nor destroyed. In another approach it can be stated as "the total energy of an isolated system remains constant.

 Ashish said: (Jan 31, 2016) Energy conservation principle is it can't be created nor it can be destroyed we can consider system having heat stored in it now we can remove heat from system and can transfer to heat sink and we can add more to it from heat source into system but we can't destroy heat.

 Sumit said: (Feb 4, 2016) According to conservation of energy principle. Energy cannot be created nor be destroyed. It can only be transferred from one source to another.

 Jivesh said: (Mar 10, 2016) According to conservation of energy principle. Energy can neither be created nor be destroyed. It can only be transferred from one form to another.

 Babatunde M. Olayinka said: (Mar 12, 2016) Energy conservation should not be confused with linear momentum. Whilst one concerns itself with the fact that energy cannot be created or lost, the other is focused on changes that can happen within a system of masses moving in a particular direction when external forces are applied. Is there a change in system energy when momentum changes? Possibly. Kinetic energy of a moving system of masses is 0.5 x (m1 x v1^2 + m2 x v2^2 x ......mn x vn^2). The mass of objects will not change unless some molecular distortion occurs which is not treated herein. However, the velocity can reduce or increase. Hence, the system energy can go up or go down. However, if this is happening in a closed system, the kinetic energy lost becomes gained as heat energy. Hence, total energy remains unchanged. But if this is not a closed system, then energy is exchanged across our artificial boundary which contains the system of masses, and therefore system energy changes. So, the key word here for the statement to be true is whether the system is CLOSED or OPEN. And, since we were not informed on this, the assumption is that it is an OPEN system in which case the correct answer is FALSE because the energy conservation principle will NOT hold in an OPEN system.

 Masiur Rahman said: (Apr 16, 2016) That question is based on newton 1st law of motion. According to this law, every body that time up to not motion then not external force are applied.

 Nikhil Varma said: (Apr 23, 2016) The rate of change of momentum is directly proportional to the applied force, as stated in the newtons second law of motion. So, the answer is A(true).

 Er. A.G.Jadhav said: (May 22, 2016) The question related to the Newtons Second law of motion, whereas the law of conservation of energy is different.

 Shubham said: (Sep 23, 2016) According to the principle of conservation of energy, the total momentum of a system of masses in Straight line remains constant unless acted upon by an external force in that direction.

 Shivanand Pal said: (Sep 27, 2016) The law of conservation of energy states that in a closed system the total amount of energy is conserved and does not change. This means that energy may change from one form to another, but that the total amount of energy in the closed system remains constant.

 Darshan Dodia said: (Oct 27, 2016) According to conservation law of energy, energy neither created nor destroyed, it changes its form from one type of energy to another type of energy.

 Yash Kumar said: (Nov 15, 2016) According to the law of conservation, all momentum of the system will remain constant in any direction without acting any force in that direction. It will change when any force will act in that direction.

 S Udaya Saradhi said: (Dec 15, 2016) If it is vacuum then external force is required to stop. If not at some point the body goes to the rest position.

 Amit said: (Dec 16, 2016) I think option (a) is correct as -> Unless force external from the system is applied the system will continue to maintain its condition of constant motion or of stationary position. Conservation of ENERGY. It's true that motion is a change in displacement, but that doesn't need the continuous addition of energy to maintain as the conditions are always IDEAL in such questions. Moreover, it's changed in motion which points toward change in energy not a change of position (Displacement). So motion in any direction is possible for a system that has a constant level of energy. (Imagine a ball in space which not in the influence of gravity from a body > if you give it a push it will start to travel with a constant velocity, NOW for this ball the total momentum of the system of masses (ball itself) in any direction remains constant unless acted upon by an external force in that direction. MEANING unless a force (or a force field) interferes with this system (WHICH (Force or force field) will be labelled EXTERNAL) the ball will go on its way beyond infinity (Literally).

 Prem Kumar said: (Dec 17, 2016) It is the law of conservation of momentum.

 Pramod Kumar said: (Dec 24, 2016) According to the law of conservation of energy, the energy neither be created nor be destroyed.

 Bharat Kumar said: (Feb 27, 2017) Depending upon its energy and its system it can changes the direction.

 Nikhul said: (Apr 8, 2017) This is by principle of conservation of linear momentum.

 Edidiong said: (May 22, 2017) Principle of conservation of energy stated that energy can neither be created nor destroy.

 Shreepatil said: (Jun 5, 2017) According to the law of conservation of energy, the energy neither be created nor be destroyed.

 Ankit said: (Jun 26, 2017) In physics, the law of conservation of energy states that the total energy of an isolated system remains constant"it is said to be conserved over time. Energy can neither be created nor destroyed; rather, it transforms from one form to another.

 Suneel Pal said: (Jul 2, 2017) Low of energy conservation is energy is a universal property and energy is not distrioid and not created only transform one form to another form.

 Peter Maina said: (Oct 16, 2017) Energy can neither be destroyed nor created.

 Afif said: (Nov 12, 2017) This is NEWTON's FIRST LAW not Principle of Conservation of energy.

 Gaurav said: (Feb 5, 2018) I think there is something missing that is friction force. If we assume newton 1st law of motion in which friction is neglected statement is true.

 Shubham said: (May 26, 2018) I am not getting this, please explain me.

 Shahbaz Ali said: (Aug 30, 2018) I am not getting this, please explain me.

 Siddharth Surendran said: (Sep 2, 2018) According to the principle of conservation of energy. Energy can neither be created nor be destroyed but can be transformed from one for to another. But here given is the principle of conservation of momentum with the tagline of conservation of energy. Therefore the answer is false.

 Adarsh Upadhyay said: (Oct 11, 2018) The law of conservation of energy is a physical law which states energy cannot be created or destroyed, but may be changed from one form to another. Another way of stating the law is to say the total energy of an isolated system remains constant or is conserved within a given frame of reference.

 Sonali said: (Mar 2, 2019) Principle of conservation of energy states that energy can neither be created nor be destroyed.

 Paatel said: (Feb 9, 2020) According to the conservation of energy, the energy neither be created and nor be destroyed it can transform one state to another state only.

 Venu said: (Apr 26, 2020) Energy neither created nor to be destroyed but it is a form of energy according to principle of the law of conservation of energy.

 Amit said: (Apr 15, 2021) Here it is Stated simply priciple of conservation of momentum, Not energy.