1
JEE Main 2019 (Online) 12th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
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)
2
JEE Main 2019 (Online) 10th April Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
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
3
JEE Main 2019 (Online) 10th April Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A solid sphere of mass M and radius R is divided into two unequal parts. The first part has a mass of $${{7M} \over 8}$$ and is converted into a uniform disc of radius 2R. The second part is converted into a uniform solid sphere. Let I1 be the moment of inertia of the disc about its axis and I2 be the moment of inertia of the new sphere about its axis. The ratio I1/I2 is given by :
A
65
B
140
C
185
D
285
4
JEE Main 2019 (Online) 10th April Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
The time dependence of the position of a particle of mass m = 2 is given by $$\overrightarrow r \left( t \right) = 2t\widehat i - 3{t^2}\widehat j$$ . Its angular momentum, with respect to the origin, at time t = 2 is
A
36 $$\widehat k$$
B
- 48 $$\widehat k$$
C
$$ - 34\left( {\widehat k - \widehat i} \right)$$
D
$$48\left( {\widehat i + \widehat j} \right)$$
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