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New answer posted

11 months ago

Physics Physics Ray Optics and Optical Instruments

Car B overtakes another car A at a relative speed of 40ms^-¹. How fast will the image of car B appear to move in the mirror of focal length 10cm fitted in car A, when the car B is 1.9m away from the car A?

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Vishal Baghel

Contributor-Level 10

For mirror

${\vec{V}}_{l_{1} M} = - m^{2} {\vec{V}}_{O_{1} M}$

${\vec{V}}_{l_{1} M}$ Velocity of image w.r.t. mirror

${\vec{V}}_{0 M}$ Velocity of object w.r.t. mirror

m magnification

$\frac{1}{v} + \frac{1}{- 1.9} = \frac{1}{- 0.1}$

$\frac{1}{v} = \frac{1}{1.9} - \frac{1}{0.1}$

$= \frac{0.1 - 1.9}{1.9 * 0.1}$

$v = \frac{1.9 * 0.1}{- 1.8} = \frac{0.19}{- 1.8} = - 0.105$

$m = - \frac{v}{u} = - (\frac{- 0.1}{- 1.9})$

$| {\vec{V}}_{l_{1} M} | = {(\frac{1}{19})}^{2} | {\vec{V}}_{O_{1} M} |$

$= \frac{1}{{(19)}^{2}} * 40 = 0.1 m / s$

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New answer posted

11 months ago

Physics Dual Nature of Radiation and Matter

In a photoelectric experiment ultraviolet light o wavelength 280nm is used with lithium cathode having work function $?$ = 2.5eV. If the wavelength of incident light is switched to 400nm, find out the change in the stopping potential. (h = 6.63 * 10^-³⁴ Js, c = 3 * 10⁸ ms^-¹)

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Vishal Baghel

Contributor-Level 10

$\frac{h c}{λ_{1}} = W + e V_{1}$

$\frac{h c}{λ_{2}} = W + e V_{2}$

$= 12400 (\frac{1}{2800} - \frac{1}{4000}) [λ_{1} & λ_{2} a r e t a k e n i n A °]$

$\begin{array}{l} = 4.4 - 3.1 \\ = 1.3 V \end{array}$

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New answer posted

11 months ago

Physics Class 12th

An electric bulb of 500 watt at 100 volt is used in a circuit having a 200V supply. Calculate resistance R to be connected in series with the bulb so that the power delivered by the bulb is 500W.

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alok kumar singh

Contributor-Level 10

As power delivered by the bulb is 500 W, potential difference across it should be 00 V. Thus,

$R = R_{b u l b} = \frac{10 0^{2}}{500} = 20 Ω$

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New answer posted

11 months ago

Physics Class 11th

Inside a uniform spherical shell:

(a) the gravitation field is zero (b) the gravitational potential is zero

(c) the gravitation field is same everywhere (d) the gravitation potential is same everywhere

(e) all the above

Choose the most appropriate answer from the options given below:

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Vishal Baghel

Contributor-Level 10

Inside a uniform spherical shell, electric field is zero every where & electric potential is constant but not zero, every where

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New answer posted

11 months ago

Physics Class 12th

Four NOR gates are connected as shown in figure. The truth table for the given figure is:

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alok kumar singh

Contributor-Level 10

$Y = \bar{(\bar{\bar{A + B}} + A) + (\bar{\bar{A + B}} + B)} + (\bar{A + B} + A) . (\bar{A + B} + B)$

A B Y

0 1

0 1 0&nbs

...more

$Y = \bar{(\bar{\bar{A + B}} + A) + (\bar{\bar{A + B}} + B)} + (\bar{A + B} + A) . (\bar{A + B} + B)$

A B Y

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0 1 0

1 0 0

1 1

less

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New answer posted

11 months ago

Physics Alternating Current

A series LCR circuit driven by 300V at a frequency of 50 Hz contains a resistance R = $3 k Ω,$ an inductor of inductive reactances X_L = 250π $Ω$ and an unknown capacitor. The value of capacitance to maximize the average power should be:

(Take π² = 10)

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Vishal Baghel

Contributor-Level 10

Power is maximum at resonance

So, $X_{L} = X_{C} = \frac{1}{ω C}$ $_{}_{} \frac{}{}$

$\Rightarrow C = \frac{1}{ω * X_{L}}$

$= \frac{1}{250 * 100 * π^{2}}$

$= 4 μ F [π^{2} = 10]$

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New answer posted

11 months ago

Physics Class 11th

A disc with a flat small bottom beaker placed on it at a distance R from its center is revolving about an axis passing through the center and perpendicular to its plane with an angular velocity $ω .$ The coefficient of static friction between the bottom of the beaker and the surface of the disc is $μ$ The beaker will revolve with the disc if :

0 Follower 7 Views

Raj Pandey

Contributor-Level 9

F. B. D of Beaker

By NLM2

$\begin{array}{l} f = m a = m ω^{2} R \\ \Rightarrow m ω^{2} R \leq μ N \\ R \leq μ g / ω^{2} \end{array}$

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New answer posted

11 months ago

Physics Physics Motion in Plane

The angle between vector $[\vec{A}] a n d (\vec{A} - \vec{B}) i s :$

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alok kumar singh

Contributor-Level 10

$t a n β = \frac{B s i n 60 °}{A - B c o s 60 °}$

$\Rightarrow β = t a n^{- 1} (\frac{\sqrt[]{3} B}{2 A - B})$

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New answer posted

11 months ago

Physics Units and Measurement

If E, L, M and G denote the quantities an energy, angular momentum, mass and constant of gravitation respectively, then the dimensions of P in the formula P = EL²M^-⁵G^-² are:-

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Vishal Baghel

Contributor-Level 10

$P = E L^{2} M^{- 5} G^{- 2}$

$= [M L^{2} T^{- 2}] {[M L^{2} T^{- 1}]}^{2} [M^{- 5}] {[M^{- 1} L^{3} T^{- 2}]}^{- 2}$

$= M^{0} L^{0} T^{0}$

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New answer posted

11 months ago

Physics Class 12th

An inductor coil stores 64J of magnetic field energy nad dissipates energy at the rate of 640W when a current of 8A is passed through it. If this coil is joined across an ideal battery, find the time constant of the circuit in seconds:

0 Follower 2 Views

Vishal Baghel

Contributor-Level 10

$U_{B} = \frac{1}{2} L l^{2} . . . . . . . . . . . . (i)$

P_R = l²R

=> 640 = (8)² R

R = $10 Ω$

from (i) 64 = $\frac{1}{2} * L * {(8)}^{2}$

L = 2H

$l = \frac{L}{R} = \frac{2}{10} = 0.2 s e c o n d$

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