1
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
$$\sqrt {{3 \over 8}} l$$
2
JEE Main 2020 (Online) 7th January Morning Slot
+4
-1
As shown in the figure, a bob of mass m is tied by a massless string whose other end portion is wound on a fly wheel (disc) of radius r and mass m. When released from rest the bob starts falling vertically. When it has covered a distance of h, the angular speed of the wheel will be:
A
$$r\sqrt {{3 \over {2gh}}}$$
B
$$r\sqrt {{3 \over {4gh}}}$$
C
$${1 \over r}\sqrt {{{4gh} \over 3}}$$
D
$${1 \over r}\sqrt {{{2gh} \over 3}}$$
3
JEE Main 2019 (Online) 12th April Morning Slot
+4
-1
A circular disc of radius b has a hole of radius a at its centre (see figure). If the mass per unit area of the disc varies as $$\left( {{{{\sigma _0}} \over r}} \right)$$ , then the radius of gyration of the disc about its axis passing through the centre is:
A
$$\sqrt {{{{a^2} + {b^2} + ab} \over 2}}$$
B
$$\sqrt {{{a + b} \over 3}}$$
C
$$\sqrt {{{{a^2} + {b^2} + ab} \over 3}}$$
D
$$\sqrt {{{a + b} \over 2}}$$
4
JEE Main 2019 (Online) 12th April Morning Slot
+4
-1
A uniform rod of length $$\ell$$ is being rotated in a horizontal plane with a constant angular speed about an axis passing through one of its ends. If the tension generated in the rod due to rotation is T(x) at a distance x from the axis, then which of the following graphs depicts it most closely?
A
B
C
D
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