1
JEE Main 2018 (Online) 15th April Evening Slot
+4
-1
When an air bubble of radius r rises from the bottom to the surface of a lake its radius becomes $${{5r} \over 4}.$$ Taking the atmospheric pressure to be equal to 10 m height of water column, the depth of the lake would approximately be (ignore the surface tension and the effect of temperature) :
A
11.2 m
B
8.7 m
C
9.5 m
D
10.5 m
2
JEE Main 2018 (Online) 15th April Evening Slot
+4
-1
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
3
JEE Main 2018 (Online) 15th April Evening Slot
+4
-1
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
4
JEE Main 2018 (Online) 15th April Evening Slot
+4
-1
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
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