Physics

Contributor-Level 10

= $l_{x x'} = [l_{y y'} + M {(\frac{5 r}{2})}^{2}] + [l_{Z Z'} + M {(\frac{13 r}{2})}^{2}]$

$M (\frac{36 r^{2}}{12}) + \frac{M * 25 r^{2}}{4} = \frac{M r^{2}}{2} + M * \frac{169 M r^{2}}{4}$

= 52 Mr²

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11 months ago

Physics Class 11th

The temperature of equals masses of three different liquids x, y and z are 10°C, 20°C and 30°C respectively. The temperature of mixture when x is mixed with y is 16°C and that when y is mixed with z is 26°C. Temperature of mixture when x and z are mixed will be:

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Contributor-Level 10

ms_x (16 – 10) = ms_y (20 – 16)

$\Rightarrow \frac{s_{x}}{s_{y}} = \frac{2}{3}$

$m s_{y} (26 - 20) = m s_{z} (30 - 26)$

$\Rightarrow \frac{s_{y}}{s_{z}} = \frac{2}{3}$

$\frac{s_{x}}{s_{z}} = \frac{s_{x}}{s_{y}} * \frac{s_{y}}{s_{z}} = \frac{2}{3} * \frac{2}{3} = \frac{4}{9}$

$m s_{x} (T - 10) = m s_{z} (30 - T)$

->4(T – 10) = 9(30 – T)

->T = 23.84°C

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11 months ago

Physics Physics Wave Optics

A source and a detector move away from each other in absence of wind with a speed of 20m/s with respect to the ground. If the detector detects a frequency of 1800 Hz of the sound coming from the source, then the original frequency of source considering speed of sound in air 340 m/s will be ……Hz.

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Physics Motion in a Straight Line

Contributor-Level 10

$f' = \frac{340 - 20}{340 + 20} * f_{0}$

$\Rightarrow 1800 = \frac{320}{360} * f_{0}$

f₀ = 2025 Hz

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11 months ago

Two spherical balls having equal masses with radius of 5cm each are thrown upwards along the same vertical direction at an interval of 3s with the same initial velocity of 35m/s, then these balls collide at a height of…………. m. (Take g = 10 m/s²)

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Contributor-Level 10

y₁ = y₂

=> $35 t - \frac{1}{2} g t^{2} = 35 (t - 3) - \frac{1}{2} g {(t - 3)}^{2}$

=> 35 * 3 = $\frac{1}{2} g (t + t - 3) * 3$

105 = $\frac{10}{2} * 3 * (2 t - 3)$

t = 5

$y_{1} = 35 * 5 - \frac{1}{2} * 10 * 5^{2}$

= 50 m

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11 months ago

A parallel-plate capacitor with plate area A has separation d between the plates. Two dielectric slabs of dielectric constant K₁ and K₂ of same area A/2 and thickness d/2 are inserted in the space between the plates. The capacitance of the capacitor will be given by:

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Contributor-Level 10

$C_{e q} = C + \frac{C_{1} . C_{2}}{C_{1} + C_{2}}$

$= \frac{ε_{0} \frac{A}{2}}{d} + \frac{\frac{k_{1} ε_{0} \frac{A}{2}}{\frac{d}{2}} . \frac{k_{2} ε_{0} \frac{A}{2}}{\frac{d}{2}}}{\frac{k_{1} ε_{0} \frac{A}{2}}{\frac{d}{2}} + \frac{k_{2} ε_{0} \frac{A}{2}}{\frac{d}{2}}}$

= $\frac{ε_{0} A}{d} (\frac{1}{2} + \frac{k_{1} k_{2}}{k_{1} + k_{2}})$

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11 months ago

What equal length of an iron wire and a copper-nickel alloy wire, each of 2mm diameter connected parallel to give an equivalent resistance of 3 $Ω$ ?

(Given resistivities of iron and copper-nickel alloy wire are $12 μ Ω$ cm and 51 $μ Ω$ cm respectively)

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Contributor-Level 10

$\frac{R_{1} R_{2}}{R_{1} + R_{2}} = 3$

$\Rightarrow \frac{(ρ_{1} \frac{l}{A}) (ρ_{2} \frac{l}{A})}{(\frac{ρ_{1} l}{A}) + (\frac{ρ_{2} l}{A})} = 3$

$= \frac{3 * [\frac{π}{4} * {(2 * 1 0^{- 3})}^{2}] [12 + 51] * 1 0^{- 6} * 1 0^{- 2}}{12 * 1 0^{- 6} * 1 0^{- 2} * 51 * 1 0^{- 6} * 1 0^{- 2}}$

$= 97$

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11 months ago

A transmitting antenna at top of a tower has a height of 50m and the height of receiving antenna is 80m. What is the range of communication for Line of Sight (LoS) mode? [use radius of earth = 6400km]

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Contributor-Level 10

Range of communication

= d₁ + d₂

= $\sqrt[]{2 R h_{T}} + \sqrt[]{2 R h_{R}}$

= $\sqrt[]{2 * 6400} (\sqrt[]{0.05} + \sqrt[]{0.08})$

= 57.28 km

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11 months ago

Statement-I: By doping silicon semiconductor with pentavalent material, the electrons density increases.

Statement-II: The n-type semiconductor has net negative charge.

In the light of the above statements, choose the most appropriate answer from the options given below:

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Physics Physics Mechanical Properties of Solids

Contributor-Level 10

Pentavalent materials have more electrons and so electron density increase. But overall semiconductor is neutral

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11 months ago

Two blocks of masses 3kg and 5kg are connected by a metal wire going over a smooth pulley. The breaking stress of the metal is $\frac{24}{π} * 1 0^{2} N m^{- 2} .$ What is the minimum radius of the wire? (take g = 10ms^-2)

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Contributor-Level 10

Tension in wire, $T = \frac{2 * 3 * 5 * 10}{3 + 5} = \frac{75}{2} N$

$\frac{T}{π r_{m i n}^{2}} = \frac{24}{π} * 1 0^{2}$

$\Rightarrow r_{m i n}^{2} = \frac{75}{2 * 24} * 1 0^{- 2} = \frac{25}{16} * 1 0^{- 2}$

$\Rightarrow r_{m i n} = \frac{5}{4} * 1 0^{- 1} m = 12.5 c m$

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11 months ago

Physics Class 11th

The initial mass of a rocket is 1000kg. Calculate at what rate the fuel should be burnt so that the rocket is given an acceleration of 20ms^-². The gases come out at a relative speed of 500ms^-¹ with respect to the rocket: [Use g = 10m/s²]

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