State if each of the following statements is true or false. Give reasons for your answer.
(a) In an elastic collision of two bodies, the momentum and energy of each body is conserved.
(b) Total energy of a system is always conserved, no matter what internal and external forces on the body are present.
(c) Work done in the motion of a body over a closed loop is zero for every force in nature.
(d) In an inelastic collision, the final kinetic energy is always less than the initial kinetic energy of the system.
State if each of the following statements is true or false. Give reasons for your answer.
(a) In an elastic collision of two bodies, the momentum and energy of each body is conserved.
(b) Total energy of a system is always conserved, no matter what internal and external forces on the body are present.
(c) Work done in the motion of a body over a closed loop is zero for every force in nature.
(d) In an inelastic collision, the final kinetic energy is always less than the initial kinetic energy of the system.
Solution and Explanation
Explanation:
(a) False : In an elastic collision, the total energy and momentum of both the bodies, and not of each individual body, is conserved.
(b) False : Although internal forces are balanced, they cause no work to be done on a body. It is the external forces that have the ability to do work. Hence, external forces are able to change the energy of a system.
(c) False : The work done in the motion of a body over a closed loop is zero for a conservation force only.
(d) True : In an inelastic collision, the final kinetic energy is always less than the initial kinetic energy of the system. This is because in such collisions, there is always a loss of energy in the form of heat, sound, etc.
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Answer carefully, with reasons :
(a) In an elastic collision of two billiard balls, is the total kinetic energy conserved during the short time of collision of the balls (i.e. when they are in contact) ?
(b) Is the total linear momentum conserved during the short time of an elastic collision of two balls ?
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Underline the correct alternative :
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(b) Work done by a body against friction always results in a loss of its kinetic/potential energy.
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Concepts Used:
Potential Energy
The energy retained by an object as a result of its stationery position is known as potential energy. The intrinsic energy of the body to its static position is known as potential energy.
The joule, abbreviated J, is the SI unit of potential energy. William Rankine, a Scottish engineer, and physicist coined the word "potential energy" in the nineteenth century. Elastic potential energy and gravitational potential energy are the two types of potential energy.
Potential Energy Formula:
The formula for gravitational potential energy is
PE = mgh
Where,
- m is the mass in kilograms
- g is the acceleration due to gravity
- h is the height in meters
Types of Potential Energy:
Potential energy is one of the two main forms of energy, along with kinetic energy. There are two main types of potential energy and they are:
- Gravitational Potential Energy
- Elastic Potential Energy