1
JEE Main 2020 (Online) 7th January Evening Slot
+4
-1
Mass per unit area of a circular disc of radius $$a$$ depends on the distance r from its centre as $$\sigma \left( r \right)$$ = A + Br . The moment of inertia of the disc about the axis, perpendicular to the plane and assing through its centre is:
A
$$2\pi {a^4}\left( {{A \over 4} + {{aB} \over 5}} \right)$$
B
$$\pi {a^4}\left( {{A \over 4} + {{aB} \over 5}} \right)$$
C
$$2\pi {a^4}\left( {{{aA} \over 4} + {B \over 5}} \right)$$
D
$$2\pi {a^4}\left( {{A \over 4} + {B \over 5}} \right)$$
2
JEE Main 2020 (Online) 7th January Morning Slot
+4
-1
The radius of gyration of a uniform rod of length $$l$$, about an axis passing through a point $${l \over 4}$$ away from the centre of the rod, and perpendicular to it, is :
A
$${1 \over 8}l$$
B
$${1 \over 4}l$$
C
$$\sqrt {{7 \over {48}}} l$$
D
$$\sqrt {{3 \over 8}} l$$
3
JEE Main 2020 (Online) 7th January Morning Slot
+4
-1
Three point particles of masses 1.0 kg, 1.5 kg and 2.5 kg are placed at three corners of a right angle triangle of sides 4.0 cm, 3.0 cm and 5.0 cm as shown in the figure. The center of mass of the system is at a point:
A
2.0 cm right and 0.9 cm above 1 kg mass
B
0.9 cm right and 2.0 cm above 1 kg mass
C
0.6 cm right and 2.0 cm above 1 kg mass
D
1.5 cm right and 1.2 cm above 1 kg mass
4
JEE Main 2019 (Online) 12th April Evening Slot
+4
-1
A smooth wire of length 2$$\pi$$r is bent into a circle and kept in a vertical plane. A bead can slide smoothly on the wire. When the circle is rotating with angular speed $$\omega$$ about the vertical diameter AB, as shown in figure, the bead is at rest with respect to the circular ring at position P as shown. Then the value of $$\omega$$2 is equal to -
A
$${{\sqrt 3 g} \over {2r}}$$
B
$${{2g} \over {\left( {r\sqrt 3 } \right)}}$$
C
$${{\left( {g\sqrt 3 } \right)} \over r}$$
D
$${{2g} \over r}$$
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Modern Physics
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