‘Friction‘ is a force that resists motion of sliding or rolling of one object moving relative to another. It is a result of the electromagnetic attraction between the charged particles of two touching surfaces. Types of Friction Static Friction : It is defined as the frictional force that acts between the surfaces when they are at rest with respect to each other. The magnitude of the static force is equal in the opposite direction when a small amount of force is applied. When the force increases, at some point maximum static friction is reached. Rolling friction : It is the force that resists motion when an object rolls on a surface. Technically it’s not friction; its ‘rolling resistance’ since when a body rolls perfectly upon a surface, on paper, there is no sliding friction between that object and surface. Sliding friction : It is the frictional force between two surfaces that are rubbing against each other. It’s a very easy and common concept. It’s hard to find a perfectly sm
Presbyopia is the gradual loss of your eyes' ability to focus on nearby objects. It's a natural, often annoying part of aging. Presbyopia usually becomes noticeable in your early to mid-40s and continues to worsen until around age 65. Symptoms of Presbyopia People commonly mistake the symptoms of presbyopia for longsightedness. However, the two conditions have different causes: longsightedness is a result of a misshapen cornea, whereas presbyopia is due to the loss of flexibility in the lens. The telltale symptom of presbyopia is blurred vision while reading, sewing, using a mobile phone, or doing anything that requires near vision. Treatment for Presbyopia There are many options for people with presbyopia, including contact lenses. Recent technologies allow people who are entering into presbyopia to continue wearing contact lenses, instead of having to switch to bifocals, or reading glasses. Common treatments for presbyopia include : Magnifiers Bifocal or varifocal spectacles