1
JEE Main 2018 (Online) 15th April Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
The value closest to the thermal velocity of a Helium atom at room temperature (300 K) in ms-1 is :
[kB =1.4 $$ \times $$ 10-23 J/K; mHe = 7 $$ \times $$ 10 -27 kg ]
A
1.3 $$ \times $$ 104
B
1.3 $$ \times $$ 103
C
1.3 $$ \times $$ 105
D
1.3 $$ \times $$ 102
2
JEE Main 2018 (Online) 15th April Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
Two simple harmonic motions, as shown below, are at right angles. They are combined to form Lissajous figures.
x(t) = A sin (at + $$\delta $$)
y(t) = B sin (bt)

Identify the correct match below.
A
Parameters   A $$ \ne $$ B, a = b; $$\delta $$ = 0;
Curve    Parabola
B
Parameters    A = B, a = b; $$\delta $$ = $${\raise0.5ex\hbox{$\scriptstyle \pi $} \kern-0.1em/\kern-0.15em \lower0.25ex\hbox{$\scriptstyle 2$}}$$
Curve    Line
C
Parameters    A $$ \ne $$ B, a = b; $$\delta $$ = $${\raise0.5ex\hbox{$\scriptstyle \pi $} \kern-0.1em/\kern-0.15em \lower0.25ex\hbox{$\scriptstyle 2$}}$$
Curve    Ellipse
D
Parameters    A = B, a = 2b; $$\delta $$ = $${\raise0.5ex\hbox{$\scriptstyle \pi $} \kern-0.1em/\kern-0.15em \lower0.25ex\hbox{$\scriptstyle 2$}}$$
Curve    Circle
3
JEE Main 2018 (Online) 15th April Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
5 beats / econd are heard when a tuning fork is sounded with a sonometer wire under tension, when the length of the sonometer wire is either 0.95 m or 1 m. The frequency of the fork will be :
A
195 Hz
B
150 Hz
C
300 Hz
D
251 Hz
4
JEE Main 2018 (Online) 15th April Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A solid ball of radius R has a charge density $$\rho $$
given by $$\rho $$ = $$\rho $$o (1 $$-$$ $${\raise0.5ex\hbox{$\scriptstyle r$} \kern-0.1em/\kern-0.15em \lower0.25ex\hbox{$\scriptstyle R$}}$$) for 0 $$ \le $$ r $$ \le $$ R. The electric field outside the ball is :
A
$${{{\rho _o}{R^3}} \over {{ \in _o}{r^2}}}$$
B
$${{{\rho _o}{R^3}} \over {12{ \in _o}{r^2}}}$$
C
$${{4{\rho _o}{R^3}} \over {3{ \in _o}{r^2}}}$$
D
$${{3{\rho _o}{R^3}} \over {4{ \in _o}{r^2}}}$$
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