Wear and tear
Encyclopedia
Wear
In materials science, wear is erosion or sideways displacement of material from its "derivative" and original position on a solid surface performed by the action of another surface....
or aging
Aging (disambiguation)
Ageing is the effect of time on a person.Aging or ageing may also refer to:* Aging , an operating system process* Aging of wine, the effect of time on wine* Ostwald ripening, precipitate or deposit aging in chemistry...
. It is used in a legal context for such areas as warranty contracts
Warranty
In business and legal transactions, a warranty is an assurance by one party to the other party that specific facts or conditions are true or will happen; the other party is permitted to rely on that assurance and seek some type of remedy if it is not true or followed.In real estate transactions, a...
from manufacturers, which usually stipulate that damage due to wear and tear will not be covered.
Wear and tear is a form of depreciation
Depreciation
Depreciation refers to two very different but related concepts:# the decrease in value of assets , and# the allocation of the cost of assets to periods in which the assets are used ....
which is assumed to occur even when an item is used competently and with care and proper maintenance
Preventive maintenance
Preventive maintenance has the following meanings:#The care and servicing by personnel for the purpose of maintaining equipment and facilities in satisfactory operating condition by providing for systematic inspection, detection, and correction of incipient failures either before they occur or...
. For example, repeated impacts may cause stress to a hammer
Hammer
A hammer is a tool meant to deliver an impact to an object. The most common uses are for driving nails, fitting parts, forging metal and breaking up objects. Hammers are often designed for a specific purpose, and vary widely in their shape and structure. The usual features are a handle and a head,...
's head. In the normal use of a hammer for its designed task, this stress is impossible to prevent, and any attempt to eliminate it would make the hammer useless. At the same time, it is expected that the normal use of a hammer will not break it beyond repair until it has gone through a certain amount of use.
The phenomenon of wear and tear is a good demonstration of the Second Law of Thermodynamics
Second law of thermodynamics
The second law of thermodynamics is an expression of the tendency that over time, differences in temperature, pressure, and chemical potential equilibrate in an isolated physical system. From the state of thermodynamic equilibrium, the law deduced the principle of the increase of entropy and...
in action - roughly speaking, objects will get messier and more worn down over time (they are said to have higher entropy
Entropy
Entropy is a thermodynamic property that can be used to determine the energy available for useful work in a thermodynamic process, such as in energy conversion devices, engines, or machines. Such devices can only be driven by convertible energy, and have a theoretical maximum efficiency when...
), unless energy from the outside world is used to fix them.
A company which supports a warranty on a product with the possibility of wear and tear will usually limit the warranty to a period of time where its wear and tear will probably not be enough to impede the use of the product significantly. Other factors such as the willingness of a customer to replace a product through warranty will affect how long the company offers it.