# Random questions: explain BB gun bullet dent in (regular) glass?

• bbgundent
In summary, the conversation discusses a dent in the front window of the speaker's house that was caused by a BB gun bullet shot from the outside. However, the dent appears to be hit from the inside. This could be explained by the transfer of energy from the outside to the inside, similar to the effect seen in Newton's cradle. The speaker also expresses concern about the potential danger of BB guns and advocates for finding and holding the person responsible accountable.
bbgundent
Hi all, this has been bugging me so maybe you can help me out.

In the front window of my house, there is a dent in the glass that looks somewhat similar to this:

http://www.flickr.com/photos/guerra/2557095422/"

However, there is not hole in the glass. But the shape of the dent is similar. The thing is, I am told that this dent was cause by a bb gun bullet that was shot FROM THE OUTSIDE, yet the dent looks like it was hit from the INSIDE (from a layman's intuition).

This seems like it could have a physics explanation but I could be wrong. Can somebody explain why this happens?

The dent from the inside looks like a crater, as in it starts out like a wide circle, and the center of this circle is it's deepest point. Hence why it is puzzzling that the bullet hit on the outside. By nature of my window I cannot examine it from the outside (it's on the second floor, etc.) but it almost appears as those the outside of the glass is not damaged, only the inside.

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BB strikes outside of glass. Outside of glass is supported against the pressure by inside of glass, passes energy along to inside. Inside of glass is not supported, dissipates energy by breaking.

A similar effect can be seen in a device called Newtons cradle. This is a pendulum like device where energy is transferred from one end of a row of balls to the other with only minimal movement of the balls in between. In your window the BB was like the ball on one end, the missign chip of glass was like the ball on the other end and the unharmed glass was like the balls in the middle.

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I have to agree with Speedy on this; the impact was probably just transferred from the outside to the inside. First order of business is to find out who did it and make the bastard pay for a new window. Criminal charges might ensue. A BB gun or pellet gun is no joke. Not only are some of them similar enough in design to be used in armed robberies, but even a very low-power device can kill a human or at least take out an eye. Whoever did it should be taken off of the street before he gets his mitts on a Tec-9 and causes some serious grief.

## 1. How does a BB gun bullet create a dent in regular glass?

When a BB gun bullet is fired at regular glass, it creates a dent due to the kinetic energy of the bullet. As the bullet hits the glass, its energy is transferred to the glass, causing a localized increase in pressure and causing the glass to deform and create a dent.

## 2. Why does a BB gun bullet create a dent in glass but not in other materials?

Glass is a brittle material, meaning it does not have a lot of elasticity or ability to bend without breaking. As a result, when a BB gun bullet hits glass, the energy from the bullet causes the glass to break and create a dent. In other materials such as metal or wood, the energy from the bullet may cause deformation or penetration rather than a dent.

## 3. Can a BB gun bullet shatter a glass window?

It is possible for a BB gun bullet to shatter a glass window, depending on the thickness and strength of the glass. If the glass is thin and not reinforced, the kinetic energy from the bullet may be enough to shatter it. However, thicker or reinforced glass may be able to withstand the impact and not shatter.

## 4. How fast does a BB gun bullet need to travel to create a dent in glass?

The speed of a BB gun bullet can vary, but it generally needs to be at least 300 feet per second (fps) to create a dent in glass. However, the exact speed needed may depend on the weight and shape of the bullet, as well as the thickness and strength of the glass.

## 5. Is it possible to remove a dent created by a BB gun bullet in glass?

It is difficult to remove a dent in glass, especially if the glass is cracked or shattered. However, some dents may be able to be repaired by a professional glass repair service using specialized tools and techniques. In most cases, it is easier and more cost-effective to replace the damaged piece of glass.

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