1
JEE Main 2019 (Online) 12th April Evening Slot
+4
-1
Three particles of masses 50 g, 100 g and 150 g are placed at the vertices of an equilateral triangle of side 1 m (as shown in the figure). The (x, y) coordinates of the centre of mass will be : A
$$\left( {{{\sqrt 3 } \over 4}m,{5 \over {12}}m} \right)$$
B
$$\left( {{7 \over {12}}m,{{\sqrt 3 } \over 8}m} \right)$$
C
$$\left( {{7 \over {12}}m,{{\sqrt 3 } \over 4}m} \right)$$
D
$$\left( {{{\sqrt 3 } \over 8}m,{7 \over {12}}m} \right)$$
2
JEE Main 2019 (Online) 12th April Morning Slot
+4
-1
A man (mass = 50 kg) and his son (mass = 20 kg) are standing on a frictionless surface facing each other. The man pushes his son so that he starts moving at a speed of 0.70 ms–1 with respect to the man. The speed of the man with respect to the surface is :
A
0.28 ms–1
B
0.47 ms–1
C
0.20 ms–1
D
0.14 ms–1
3
JEE Main 2019 (Online) 10th April Evening Slot
+4
-1
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
+4
-1
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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