1
JEE Main 2021 (Online) 17th March Morning Shift
+4
-1
A mass M hangs on a massless rod of length l which rotates at a constant angular frequency. The mass M moves with steady speed in a circular path of constant radius. Assume that the system is in steady circular motion with constant angular velocity $$\omega$$. The angular momentum of M about point A is LA which lies in the positive z direction and the angular momentum of M about point B is LB. The correct statement for this system is :

A
LA is constant, both in magnitude and direction
B
LB is constant in direction with varying magnitude
C
LB is constant, both in magnitude and direction
D
LA and LB are both constant in magnitude and direction
2
JEE Main 2021 (Online) 16th March Morning Shift
+4
-1
A block of 200 g mass moves with a uniform speed in a horizontal circular groove, with vertical side walls of radius 20 cm. If the block takes 40 s to complete one round, the normal force by the side walls of the groove is :
A
9.859 $$\times$$ 10$$-$$2 N
B
0.0314 N
C
9.859 $$\times$$ 10$$-$$4 N
D
6.28 $$\times$$ 10$$-$$3 N
3
JEE Main 2021 (Online) 16th March Morning Shift
+4
-1
The maximum and minimum distances of a comet from the Sun are 1.6 $$\times$$ 1012 m and 8.0 $$\times$$ 1010 m respectively. If the speed of the comet at the nearest point is 6 $$\times$$ 104 ms$$-$$1, the speed at the farthest point is :
A
3.0 $$\times$$ 103 m/s
B
6.0 $$\times$$ 103 m/s
C
1.5 $$\times$$ 103 m/s
D
4.5 $$\times$$ 103 m/s
4
JEE Main 2021 (Online) 26th February Evening Shift
+4
-1
A cord is wound round the circumference of wheel of radius r. The axis of the wheel is horizontal and the moment of inertia about it is I. A weight mg is attached to the cord at the end. The weight falls from rest. After falling through a distance 'h', the square of angular velocity of wheel will be :
A
$${{2mgh} \over {I + 2m{r^2}}}$$
B
$${{2mgh} \over {I + m{r^2}}}$$
C
2gh
D
$${{2gh} \over {I + m{r^2}}}$$
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