1
JEE Main 2019 (Online) 11th January Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A slab is subjected to two forces $$\overrightarrow {{F_1}} $$ and $$\overrightarrow {{F_2}} $$ of same magnitude F as shown in the figure. Force $$\overrightarrow {{F_2}} $$ is in XY-plane while force $$\overrightarrow {{F_1}} $$ acts along z = axis at the point $$\left( {2\overrightarrow i + 3\overrightarrow j } \right).$$. The moment of these forces about point O will be :

JEE Main 2019 (Online) 11th January Morning Slot Physics - Rotational Motion Question 170 English
A
$$\left( {3\widehat i - 2\widehat j - 3\widehat k} \right)F$$
B
$$\left( {3\widehat i + 2\widehat j - 3\widehat k} \right)F$$
C
$$\left( {3\widehat i + 2\widehat j + 3\widehat k} \right)F$$
D
$$\left( {3\widehat i - 2\widehat j + 3\widehat k} \right)F$$
2
JEE Main 2019 (Online) 10th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
A rigid massless rod of length 3l has two masses attached at each end as shown in the figure. The rod is pivoted at point P on the horizontal axis (see figure). When released from initial horizontal position, its instantaneous angular acceleration will be -

JEE Main 2019 (Online) 10th January Evening Slot Physics - Rotational Motion Question 172 English
A
$${g \over {13l}}$$
B
$${g \over {2l}}$$
C
$${g \over {3l}}$$
D
$${7g \over {3l}}$$
3
JEE Main 2019 (Online) 10th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
Two identical spherical balls of mass M and radius R each are stuck on two ends of a rod of length 2R and mass M (see figure). The moment of inertia of the system about the axis passing perpendicularly through the centre of the rod is :

JEE Main 2019 (Online) 10th January Evening Slot Physics - Rotational Motion Question 171 English
A
$${{17} \over {15}}$$ MR2
B
$${{137} \over {15}}$$ MR2
C
$${{209} \over {15}}$$ MR2
D
$${{152} \over {15}}$$ MR2
4
JEE Main 2019 (Online) 10th January Morning Slot
MCQ (Single Correct Answer)
+4
-1
Change Language
To mop-clean a floor, a cleaning machine presses a circular mop of radius R vertically down with a total force F and rotates it with a constant angular speed about its axis. If the force F is distributed uniformly over the mop and if coefficient of friction between the mop and the floor is $$\mu $$, the torque, applied by the machine on the mop is -
A
$$\mu $$FR/2
B
$$\mu $$FR/3
C
$$\mu $$FR/6
D
$${2 \over 3}$$$$\mu $$FR
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