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Can a polyhedron have following for its faces
(i) 3 triangles?
(ii) 4 triangles?
(iii) a square and four triangles?
(i) 3 triangles?
(ii) 4 triangles?
(iii) a square and four triangles?
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Can a polyhedron have following for its faces
(i) 3 triangles?
(ii) 4 triangles?
(iii) a square and four triangles?
(i) 3 triangles?
(ii) 4 triangles?
(iii) a square and four triangles?
Answer
1) No.
2) Yes,
3) Yes.
2) Yes,
3) Yes.
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Solution
(i) For a polyhedron, minimum number of faces required are four, so three triangles cannot form a polyhedron.
(ii) Yes, a polyhedron can have 4 triangles as its faces, which is the case in a Tetrahedron.
(iii) Yes, a square pyramid is a polyhedron which has a square and four triangles as its faces.
(ii) Yes, a polyhedron can have 4 triangles as its faces, which is the case in a Tetrahedron.
(iii) Yes, a square pyramid is a polyhedron which has a square and four triangles as its faces.
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The dimensions \({M}{L}^{{-{{1}}}}{T}^{{-{{2}}}}\) may correspond to
(A) work done by a force
(B) linear momentum
(C) pressure
(D) energy per unt volume
(A) work done by a force
(B) linear momentum
(C) pressure
(D) energy per unt volume
A block of side \({0.5}{m}\) is \({30}\%\) submerged in a liquid of density \({1}{g}{m}/{\left({c}{c}\right)}\). Then find mass of an object placed on block for complete submergence.
(A) \({87.3}{k}{g}\)
(B) \({85.3}{k}{g}\)
(C) \({82.3}{k}{g}\)
(D) \({80.3}{K}{G}\)
(A) \({87.3}{k}{g}\)
(B) \({85.3}{k}{g}\)
(C) \({82.3}{k}{g}\)
(D) \({80.3}{K}{G}\)
A small, conducting circular loop is placed inside a long solenoid carrying a current. The plane of the loop contains the axis of the solenoid. If the current in the solenoid is varied, the current induced in the loop is
(A) clock wise
(B) anticlockwise
(C) zero
(D) clockwise or anticlockwise depending on whether the resistance is increased or decreased.
(A) clock wise
(B) anticlockwise
(C) zero
(D) clockwise or anticlockwise depending on whether the resistance is increased or decreased.
Calculate the saturation thermionic current if \({120}{W}\) is applied to a thoriated-tungsten filament of surface area \({1.0}{c}{m}^{{2}}\). Assume that the surface radiates like a blackbody. The required constants are
\({A}={3}\times{10}^{{4}}{A}{m}^{{-{2}}}-{K}^{{2}}\), \(\varphi={2.6}{e}{V},{k}={8.62}\times{10}^{{-{5}}}{e}{V}{k}{K}^{{-{1}}}\)
and \(\sigma={6}\times{10}^{{-{8}}}{W}{m}^{{-{2}}}{K}^{{-{4}}}\)
\({A}={3}\times{10}^{{4}}{A}{m}^{{-{2}}}-{K}^{{2}}\), \(\varphi={2.6}{e}{V},{k}={8.62}\times{10}^{{-{5}}}{e}{V}{k}{K}^{{-{1}}}\)
and \(\sigma={6}\times{10}^{{-{8}}}{W}{m}^{{-{2}}}{K}^{{-{4}}}\)
A lift is moving down with acceleration a. A man in the lift drops a ball inside the lift. The acceleration of the ball as observed by the man in the lift and a man standing stationary on the ground are respectively
(a) g,g
(b) g-a, g-a
(c) g-a, g
(d) a,g
(a) g,g
(b) g-a, g-a
(c) g-a, g
(d) a,g
If the resultant of all the external forces acting on a system of particles is zero. Then from an inertial frame, one can surely say that
(A) linearmomentum of the system does not change in time
(B) kinetic energy of the system does not change in time
(C) angular momentum of the system does not chagne in time
(D) potential energy of the system does not change in time
(A) linearmomentum of the system does not change in time
(B) kinetic energy of the system does not change in time
(C) angular momentum of the system does not chagne in time
(D) potential energy of the system does not change in time
Electrons in a conductor have no motion in the absence of a potential difference across it.
Atoms having the same …… but different ….. Are colled isotopes .
Scienists are working hard to develop inclear fusion reactor Nocies of heavy hydrogen, \(_{\left({1}\right)}^{{{2}}}{H}\) , known as deuteron and denoted by \({D}\), can be thought of as a candidate for fusion rector . The \({D}-{D}\) reaction is \(_{\left({1}\right)}^{{{2}}}{H}{+_{{{1}}}^{{{2}}}}{H}{\rightarrow_{{{2}}}^{{{1}}}}{H}{e}+{n}+{e}\ne{r}{g}{y}\) in the core of fasion reactor a gas of heavy hydrogen of \(_{\left({1}\right)}^{{{2}}}{H}\) nucles and electrons is know as plasma . The nuclei move randonity in the reactor to take place Unally , the temperature in the reactor core are too ligh and to natrual will can be used to confine the to pleama for a time l_(0) before the particles by away from the case if \({n}\) is the denasity (number volume ) of determines , the product\({n}{t}_{{{0}}}\)is called Lavson number in one of the criteria , a reactor is termed successful if Lawson number is greater then \({5}\times{10}^{{{14}}}{s}/{c}{m}^{{{2}}}\)
it may be helpfull to use the following botczmann constant
\(\lambda={8.6}\times{10}^{{-{5}}}{e}{V}/{k},\frac{{{e}^{{{2}}}}}{{{4}\pi{s}_{{{0}}}}}={1.44}\times{10}^{{-{9}}}{e}{V}{m}\)
Result of calulations for fopur different desine of a fasion reactor using \({D}-{D}\) reaction are given below which of these is most promising based on Lawson crierion ?
(A) deuteron density \(={2.0}\times{10}^{{{12}}}{c}{m}^{{-{3}}}\),
confinement time \(={5.0}\times{10}^{{-{3}}}{s}\)
(B) deuteron density \(={8.0}\times{10}^{{{14}}}{c}{m}^{{-{3}}}\),
confinement time \(={9.0}\times{10}^{{-{1}}}{s}\)
(C) deuteron density \(={4.0}\times{10}^{{{23}}}{c}{m}^{{-{3}}}\),
confinement time \(={1.0}\times{10}^{{-{11}}}{s}\)
(D) deuteron density \(={1.0}\times{10}^{{{24}}}{c}{m}^{{-{3}}}\)
confinement time \(={4.0}\times{10}^{{-{12}}}{s}\)
it may be helpfull to use the following botczmann constant
\(\lambda={8.6}\times{10}^{{-{5}}}{e}{V}/{k},\frac{{{e}^{{{2}}}}}{{{4}\pi{s}_{{{0}}}}}={1.44}\times{10}^{{-{9}}}{e}{V}{m}\)
Result of calulations for fopur different desine of a fasion reactor using \({D}-{D}\) reaction are given below which of these is most promising based on Lawson crierion ?
(A) deuteron density \(={2.0}\times{10}^{{{12}}}{c}{m}^{{-{3}}}\),
confinement time \(={5.0}\times{10}^{{-{3}}}{s}\)
(B) deuteron density \(={8.0}\times{10}^{{{14}}}{c}{m}^{{-{3}}}\),
confinement time \(={9.0}\times{10}^{{-{1}}}{s}\)
(C) deuteron density \(={4.0}\times{10}^{{{23}}}{c}{m}^{{-{3}}}\),
confinement time \(={1.0}\times{10}^{{-{11}}}{s}\)
(D) deuteron density \(={1.0}\times{10}^{{{24}}}{c}{m}^{{-{3}}}\)
confinement time \(={4.0}\times{10}^{{-{12}}}{s}\)
The energy band gap is maximum in
(A) metals
(B) superoonductors
(C) insulators
(D) semiconductors
(A) metals
(B) superoonductors
(C) insulators
(D) semiconductors
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