1
JEE Main 2019 (Online) 12th April Morning Slot
MCQ (Single Correct Answer)
+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: JEE Main 2019 (Online) 12th April Morning Slot Physics - Rotational Motion Question 126 English
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
$$\sqrt {{{a + b} \over 2}} $$
2
JEE Main 2019 (Online) 12th April Morning Slot
MCQ (Single Correct Answer)
+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
JEE Main 2019 (Online) 12th April Morning Slot Physics - Rotational Motion Question 125 English Option 1
B
JEE Main 2019 (Online) 12th April Morning Slot Physics - Rotational Motion Question 125 English Option 2
C
JEE Main 2019 (Online) 12th April Morning Slot Physics - Rotational Motion Question 125 English Option 3
D
JEE Main 2019 (Online) 12th April Morning Slot Physics - Rotational Motion Question 125 English Option 4
3
JEE Main 2019 (Online) 12th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
A person of mass M is, sitting on a swing of length L and swinging with an angular amplitude $$\theta $$0. If the person stands up when the swing passes through its lowest point, the work done by him, assuming that his center of mass moves by a distance $$\ell $$($$\ell $$ << L), is close to;
A
mg$$\ell $$(1 + $$\theta $$02)
B
mg$$\ell $$
C
mg$$\ell $$(1 + $${{\theta _0^2} \over 2}$$)
D
mg$$\ell $$(1 - $$\theta $$02)
4
JEE Main 2019 (Online) 10th April Evening Slot
MCQ (Single Correct Answer)
+4
-1
A metal coin of mass 5 g and radius 1 cm is fixed to a thin stick AB of negligible mass as shown in the figure. The system is initially at rest. The constant torque, that will make the system rotate about AB at 25 rotations per second in 5s, is close to : JEE Main 2019 (Online) 10th April Evening Slot Physics - Rotational Motion Question 129 English
A
7.9 × 10–6 Nm
B
4.0 × 10–6 Nm
C
2.0 × 10–5 Nm
D
1.6 × 10–5 Nm
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