Most of us wear shades to protect our eyes from sun and dust but some of us wear it to amp up our personality. But have you ever wondered why security guards and wear sunglasses?That too in black colour.We will discuss the reason behind this in the following article.

1. Misleads attackers

Security personnel keep their eyes roving across the entire area all the time. Wearing sunglasses ensures that attackers cannot see the eyes of the guard and do not know which way to move. It helps the security guards sense sudden movement better.

2. Protection in case of blasts

In case of any untoward incident like bomb blast or firing, it's natural that eyes of a person may get closed for a while, but security guards can’t afford to close their eyes in these crucial situations and these sunglasses help them in keeping their eyes open all the time whenever they are with the VIPs.

3. Help protect from external objects

If the field or open space is particularly foggy or dusty, then the glasses shield the wearer’s eyes and help them see clearly even during the haze. The primary aim of the guards or the security is to protect the target from an unwarranted attack and at such times, they need to be extremely alert – especially if it is an open ground.

4. To avoid glares from sunlight or direct flashes

Dark glasses help avoid direct sunlight and glares and also give the eye a neutral black tone making it easy to see beyond colour restrictions. It helps the security personnel blink less and keep eyes open for longer period.

5.To hide their emotions

As cliched as it may sound, wearing sunglasses helps the wearer protect his eyes from emotion. Even if the other person managed to surprise or shock him, the attacker won’t be able to see the shock as the sunglasses will hide the eyes. It helps the wearer to recover quickly and plan a counter-attack without giving the attacker an upper hand.


You might have noticed that most manholes, and their covers, are round in shape.We will discuss the reason behind the round shape of manhole cover in this article.

1.Mishandling the Manhole cover-A round manhole cover cannot fall through its circular opening, whereas a square manhole cover could fall in if it were inserted diagonally in the hole.

2. Rolling the Manhole Cover -A round manhole cover is easily moved and rolled.

3. Strongest shape-When a square or rectangular manhole cover is subjected to sudden vertical compression (think of a very heavy truck driving over it), the weakest spot, the center, isn't equidistant to all supporting sides, especially the corners, which give support from two directions and are thus the strongest points (for similar reasons, experts recommend you stand in the corner of a room during an earthquake). With a circular cover, the center is equidistant from all supporting sides, and due to the gradual curve, any point along the edge gives almost as much support as a corner on a square cover. Circular shape results in uniform stress distribution.

4. Circular covers don’t need to be rotated or precisely aligned when placing them on the opening.

5. Round tubes are the strongest shape against the compression of the earth around them, so the cover of the tube would naturally be round as well.

6. It’s easier to dig a circular hole.


You might have seen all two-wheelers which are launched after 2017 have their headlights always ON, we do not have an option to turn it OFF. In this article, we will discuss the reason behind always ON headlight in two-wheelers.

All new motorcycles and scooters that roll into the market need to feature AHO from April 1st, 2017 onwards. Most two-wheeler manufacturers term AHO as All-time Headlight On or Automatic Headlight On system. As the name suggests, new motorcycles and scooters which are sold and registered after April 1st, 2017 need to have the headlights on at all times. Yes, even during the day.

This is in compliance to a notice issued by the Road and Transport Ministry of India. All new bikes equipped AHO will not have a button to switch on the headlight, since it will always be on, but will only get high-beam and low-beam buttons along with the pass switch.

Why headlights need to be turned ON always:

This is a safety measure initiated by the ministry and is followed in many international countries. The idea behind this is that keeping headlights on throughout the day, even when the sun is nice and bright, makes spotting two-wheelers easier on the road. So, others on the road can see the motorcycle or scooter from a distance. It is also helpful during tricky light conditions during dusk, dawn or in case of sudden clouds casting a shadow. In short, it is a safety measure to increase the visibility of the two-wheelers on the road so that accidents can be prevented.

This will strain two-wheeler batteries a little more, but without hampering the battery in any way. Most modern motorcycles and scooters use advanced battery and alternators system, which can comfortably manage the extra load. This will no way alter fuel economy either. So, no need to worry.

Now-a-days most of the companies are coming up with DRL (Day-time Running Lights) on their motorcycle headlights as seen on the Bajaj Platina. This is basically a small, but fairly bright strip of light incorporated in the headlight console. This strip remains illuminated even if the headlight isn’t switched on, so that the on-coming traffic can clearly see the motorcycle or scooter approaching.


Washers are often used in conjunction with threaded fasteners. Washers consist of a flattened, circular- or disc-shaped piece of metal with a hole in the middle. Skipping on washers can dramatically reduce the lifespan of how your product is put together. Ultimately, that leads to disaster for the product itself. Not just any washer will do for all applications. Once you understand that, you can give washers the respect they deserve. In this article, we will discuss the use of washers with respect to nut and bolts.

Load Distribution

The primary purpose of most washers is to evenly distribute the load of the threaded fastener with which they are used. Threaded fasteners stress the material in which they are driven. For example, driving a screw into the wood may cause the wood to crack around the surface. Washers reduce the risk of such damage by evenly distributing the fastener’s load across the surface of the material. Not all materials require the use of washers. 

But for wood and other relatively soft materials, washers are useful to protect against stress-related damage when the threaded fastener is driven into the material.


Washers can also be used as spacers. If the threaded fastener is longer than the depth of the object, you won’t be able to drive it all the way into the object — not without having some of the fastener stick out the back of the object, at least. Driving a 4-inch screw into an object that’s 3 inches deep will result in 1 inch of the screw’s tip protruding out of the back of the object. 
A simple solution to this problem is to use washers. Placing washers through the threaded fastener before driving it into the object creates padding so that the fastener doesn’t go too deep.

Vibration Absorption

Certain types of washers are designed to absorb vibrations. Known as vibration damping or vibration-isolating washers, they usually aren’t made of metal. Instead, they are made of a softer material like plastic, rubber or urethane. Softer materials such as these are more effective at absorbing vibrations than hard materials, including metal.

If a threaded fastener is being used to connect two objects, and one of those objects producing vibrates aggressively, using vibration-damping washers can protect the other object from damage.

Liquid Protection

Other types of washers prevent the ingress of water and liquids. They are often used in water pipes and connections to create a waterproof seal. Like vibration-damping washers, liquid-sealing washers are made of a soft material that’s able to press completely against the surface of the object.


You might have seen an Emergency pull chain in Railways. The chain is used to stop the train at the time of an Emergency. Most of us though know what the Pull chain is been used for but do not know the exact mechanism of it. Here is a brief description of what exactly happens in a Train when you pull the Emergency chain.

In a Typical Indian train, the coaches are interconnected by two pipe hoses. The alarm pull chain is in continuity with the Brake pipe (As in the Schematic diagram below) constantly maintained at specific air pressure.
Whenever the chain is been pulled some Air (earlier vacuum drop was used) escapes from the Passenger Emergency Alarm Valve ( PEAV ) vent. 

This drop in pressure results in the application of the brake cylinder/piston assembly in the bogie of the coach, which starts pressing the brake pads on the wheels or disc of the entire train. The loco pilot also notices the air pressure drop in the gauge and then uses his own skills to help the train stop comfortably.

As soon as there is pressure drop, the driver whistles in "two short one long" to indicate to the guard and the train TTEs that there has been Alarm chain pulling.

The guard's compartment also has the air pressure gauge which gives him an indication.

Also recently the coaches have been fitted with emergency flashers on the sidewalls of the coaches, and these flashers are also activated when the brake pipe pressure is lost for any reason other than the driver's application of the brakes.

Assistant Driver and Guard find out in which coach the ACP actually occurred and help to "put right" the concerned coach i.e. the lever needs to be manually reset that helps to release the brakes of that coach. Until this is done, the lamp and buzzer in the locomotive cab are continuously activated. The air pressure system again builds up air pressure and that releases all brakes of all coach and the train gets ready to depart.


You might have noticed that buckets generally have a conical or frustum like shape. Have you ever wondered why is it designed so? Why not any other shape?
We will discuss the reason behind the conical shape of the bucket in this article.

The bucket is designed in conical shape due to the following reasons:

1.)A bucket is typically used to put something in, e.g. you dip a mug in it or wash something in it. This means having a large top area is useful for easy access.

2.)It makes it easy to hold or lift the bucket of such shape as any other shape like a cylinder or frustum upside down will have the chances of slipping down.

3.)The center of gravity of frustum shape is such that it provides the least effort and easy means to lift it.

4.)While pouring down the water or liquid out, the frustum of the cone-shaped bucket provides easy grabbing and balance and comfort.

5.)This shape allows multiple buckets to be stacked (nested) inside each other, providing both dense and secure storage of large numbers of buckets.

Compared to the cylinder, a frustum shape gives maximum weight distribution while lifting thus minimum effort is used while lifting bucket of frustum shape.


You might have noticed that the watches and clocks found in product photographs and advertisements usually show the time 10:10.Have you wondered the reason behind this.We will discuss the reason for this in this article.

These are some reasons why exactly this time is chosen.According to the New York Times, the main reason is quite simple and obvious: aesthetics. There are a number of visual advantages to having the hands set at the 10:10 positions.

1.)One is that the hands are kept from overlapping at this position. Having them on both sides of the watch face ensures that the hands themselves are visible and can be appreciated.

2.)When we look at a watch at 10:10, we consider as if the watch is smiling. It is lovely to have a smiling face, rather than having a crying face when the time is at 8:20. So the form of the hands has a positive effect on the view.

 3.)The arrangement of the hands is symmetrical, which people generally find more pleasant than asymmetry, making the product more appealing to customers.

4.) The manufacturer's logo, usually is in the center of the face under the 12, is not only visible but nicely framed when the needles are positioned at 10:10.

5.) Additional elements on the face (like date windows or secondary dials), usually placed near the 3, 6, or 9, won't be obscured.

There are a number of urban legends regarding the 10:10 time floating around in the world. Many of them attribute it to a historic event (e.g. Lincoln/JFK assassinations, the dropping of the atomic bombs), but there isn’t any truth behind those explanations.