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<meta name="description" content="a. A rod of length l is made of explosive material. The detonation velocity (the rate of involvement in the explosion of new parts of the explosive) is equal to v, and the rate of spreading of the products of the explosion is u < v. How does the region occupied by the products of the explosion change with time if the rod is detonated at one end? Make a drawing.">
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<meta property="og:description" content="a. A rod of length l is made of explosive material. The detonation velocity (the rate of involvement in the explosion of new parts of the explosive) is equal to v, and the rate of spreading of the products of the explosion is u < v. How does the region occupied by the products of the explosion change with time if the rod is detonated at one end? Make a drawing.">
<title>a. A rod of length l is made of explosive material. The detonation velocity (the rate of involvement in the explosion of new parts of the explosive) is equal to v, and the rate of spreading of the products of the explosion is u < v. How does the region occupied by the products of the explosion change with time if the rod is detonated at one end? Make a drawing.</title>
$1.1.9.$ a. A rod of length $l$ is made of explosive material. The detonation velocity (the rate of involvement in the explosion of new parts of the explosive) is equal to $v$, and the rate of spreading of the products of the explosion is $u < v$. How does the region occupied by the products of the explosion change with time if the rod is detonated at one end? Make a drawing.
</p>
<p>
b. From the same explosive material it is necessary to make such a thin-walled conical shell so that when detonating it from the top, the products of the explosion simultaneously hit the rod on the axis of the cone. What angle between the axis of the cone and the generatrix should be chosen?
<center>
<figure>
<img src="statement.png"
loading="lazy" width="230" />
<figcaption>
For problem 1.1.9
</figcaption>
</figure>
</center>
</p>
<h3>Solution</h3>
<p>
<center>
<figure>
<img src="solution.png" alt="1.1.9"
loading="lazy" width="300" />
<figcaption>
Figure to part a)
</figcaption>
</figure>
</center>
<p>
1. The configuration of the region occupied by the products of the explosion until the moment of complete oxidation of the rod, at $\tau < L/v$ will have the form of a cone of height $h = vt$, the base of which is a hemisphere of radius $R = u \cdot t$.
</p>
<p>
2. After the rod oxidation is over, i.e. for time $\tau\geq L/v$, the product region will be bounded by two hemispheres with radii
</p>
<p style="text-align: center;">
$$R=ut \text{ и }r=u(t-\frac{L}{v})$$
</p>
<br>
<center>
<figure>
<img src="1.1.9(b).png" alt="1.1.9"
loading="lazy" width="250" />
<figcaption>
Figure to part b)
</figcaption>
</figure>
</center>
<p>
1. If the length of the cone's trunk is $L$, then its height $h$ is determined by Eq.
</p>
<p style="text-align: center;">
$$h = L \cdot cos \alpha$$
</p>
<p>
from where
</p>
<p style="text-align: center;">
$$L = \frac{h}{cos \alpha}$$
</p>
<p>
2. According to the problem condition $t_1=t_2$, i.e.
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<meta name="keywords" content="Savchenko Problems in Physics, Savchenko solutions, physics problems, physics olympiad preparation, IPhO, Jaan Kalda">
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<meta name="description" content="The largest dataset of solutions of 'Savchenko. Problems in Physics'. Savchenko’s Problems in General Physics is widely used to prepare for olympiads and it is a useful tool to
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master and sharpen your skills and techniques in comptetitive problem solving. Some of these problems were a source
of inspiration for Jaan Kalda’s handouts and to some NBPhO problems. You may find problems from old IPhO
<meta property="og:title" content="a. A rod of length l is made of explosive material. The detonation velocity (the rate of involvement in the explosion of new parts of the explosive) is equal to v, and the rate of spreading of the products of the explosion is u < v. How does the region occupied by the products of the explosion change with time if the rod is detonated at one end? Make a drawing.">
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<meta property="og:description" content="a. A rod of length l is made of explosive material. The detonation velocity (the rate of involvement in the explosion of new parts of the explosive) is equal to v, and the rate of spreading of the products of the explosion is u < v. How does the region occupied by the products of the explosion change with time if the rod is detonated at one end? Make a drawing.">
<title>a. A rod of length l is made of explosive material. The detonation velocity (the rate of involvement in the explosion of new parts of the explosive) is equal to v, and the rate of spreading of the products of the explosion is u < v. How does the region occupied by the products of the explosion change with time if the rod is detonated at one end? Make a drawing.</title>
$1.1.9.$ a. A rod of length $l$ is made of explosive material. The detonation velocity (the rate of involvement in the explosion of new parts of the explosive) is equal to $v$, and the rate of spreading of the products of the explosion is $u < v$. How does the region occupied by the products of the explosion change with time if the rod is detonated at one end? Make a drawing.
$1.1.9.$ a. A rod of length $l$ is made of explosive material. The detonation velocity (the rate of involvement in the explosion of new parts of the explosive) is equal to $v$, and the rate of spreading of the products of the explosion is $u < v$. How does the region occupied by the products of the explosion change with time if the rod is detonated at one end? Make a drawing.
</p>
</p>
<p>
<p>
b. From the same explosive material it is necessary to make such a thin-walled conical shell so that when detonating it from the top, the products of the explosion simultaneously hit the rod on the axis of the cone. What angle between the axis of the cone and the generatrix should be chosen?
b. From the same explosive material it is necessary to make such a thin-walled conical shell so that when detonating it from the top, the products of the explosion simultaneously hit the rod on the axis of the cone. What angle between the axis of the cone and the generatrix should be chosen?
<center>
<center>
<figure>
<figure>
<img src="statement.png"
<img src="statement.png"
loading="lazy" width="230" />
loading="lazy" width="230" />
<figcaption>
<figcaption>
For problem 1.1.9
For problem 1.1.9
</figcaption>
</figcaption>
</figure>
</figure>
</center>
</center>
</p>
</p>
<h3>Solution</h3>
<h3>Solution</h3>
<p>
<p>
<center>
<center>
<figure>
<figure>
<img src="solution.png" alt="1.1.9"
<img src="solution.png" alt="1.1.9"
loading="lazy" width="300" />
loading="lazy" width="300" />
<figcaption>
<figcaption>
Figure to part a)
Figure to part a)
</figcaption>
</figcaption>
</figure>
</figure>
</center>
</center>
<p>
<p>
1. The configuration of the region occupied by the products of the explosion until the moment of complete oxidation of the rod, at $\tau < L/v$ will have the form of a cone of height $h = vt$, the base of which is a hemisphere of radius $R = u \cdot t$.
1. The configuration of the region occupied by the products of the explosion until the moment of complete oxidation of the rod, at $\tau < L/v$ will have the form of a cone of height $h = vt$, the base of which is a hemisphere of radius $R = u \cdot t$.
</p>
</p>
<p>
<p>
2. After the rod oxidation is over, i.e. for time $\tau\geq L/v$, the product region will be bounded by two hemispheres with radii
2. After the rod oxidation is over, i.e. for time $\tau\geq L/v$, the product region will be bounded by two hemispheres with radii
</p>
</p>
<p style="text-align: center;">
<p style="text-align: center;">
$$R=ut \text{ и }r=u(t-\frac{L}{v})$$
$$R=ut \text{ и }r=u(t-\frac{L}{v})$$
</p>
</p>
<br>
<br>
<center>
<center>
<figure>
<figure>
<img src="1.1.9(b).png" alt="1.1.9"
<img src="1.1.9(b).png" alt="1.1.9"
loading="lazy" width="250" />
loading="lazy" width="250" />
<figcaption>
<figcaption>
Figure to part b)
Figure to part b)
</figcaption>
</figcaption>
</figure>
</figure>
</center>
</center>
<p>
<p>
1. If the length of the cone's trunk is $L$, then its height $h$ is determined by Eq.
1. If the length of the cone's trunk is $L$, then its height $h$ is determined by Eq.
</p>
</p>
<p style="text-align: center;">
<p style="text-align: center;">
$$h = L \cdot cos \alpha$$
$$h = L \cdot cos \alpha$$
</p>
</p>
<p>
<p>
from where
from where
</p>
</p>
<p style="text-align: center;">
<p style="text-align: center;">
$$L = \frac{h}{cos \alpha}$$
$$L = \frac{h}{cos \alpha}$$
</p>
</p>
<p>
<p>
2. According to the problem condition $t_1=t_2$, i.e.
2. According to the problem condition $t_1=t_2$, i.e.
<small>All rights belong to the authors. <br> Commercial use of materials - with the written permission of the authors. <br> astrosander01@gmail.com <br></small>
<small>All rights belong to the authors. <br> Commercial use of materials - with the written permission of the authors. <br> astrosander01@gmail.com <br></small>
