1
JEE Main 2019 (Online) 9th April Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A thin smooth rod of length L and mass M is rotating freely with angular speed $$\omega $$0 about an axis perpendicular to the rod and passing through its center. Two beads of mass m and negligible size are at the center of the rod initially. The beads are free to slide along the rod. The angular speed of the system , when the beads reach the opposite ends of the rod, will be :-
A
$${{M{\omega _0}} \over {M + 3m}}$$
B
$${{M{\omega _0}} \over {M + m}}$$
C
$${{M{\omega _0}} \over {M + 6m}}$$
D
$${{M{\omega _0}} \over {M + 2m}}$$
2
JEE Main 2019 (Online) 9th April Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A string 2.0 m long and fixed at its ends is driven by a 240 Hz vibrator. The string vibrates in its third harmonic mode. The speed of the wave and its fundamental frequency is :-
A
180m/s, 80 Hz
B
180m/s, 120 Hz
C
320m/s, 120 Hz
D
320m/s, 80 Hz
3
JEE Main 2019 (Online) 9th April Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
In a conductor, if the number of conduction electrons per unit volume is 8.5 × 1028 m–3 and mean free time is 25ƒs (femto second), it's approximate resistivity is :-
(me = 9.1 × 10–31 kg)
A
10–8 $$\Omega $$m
B
10–7 $$\Omega $$m
C
10–5 $$\Omega $$m
D
10–6 $$\Omega $$m
4
JEE Main 2019 (Online) 9th April Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
The parallel combination of two air filled parallel plate capacitors of capacitance C and nC is connected to a battery of voltage, V. When the capacitors are fully charged, the battery is removed and after that a dielectric material of dielectric constant K is placed between the two plates of the first capacitor. The new potential difference of the combined system is :-
A
V
B
$${V \over {K + n}}$$
C
$${{(n+1)V} \over {K + n}}$$
D
$${{nV} \over {K + n}}$$
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