1
WB JEE 2018
MCQ (Single Correct Answer)
+1
-0.25
Change Language
In a triangle ABC, the sides AB and AC are represented by the vectors $$3\widehat i + \widehat j + \widehat k$$ and $$\widehat i + 2\widehat j + \widehat k$$, respectively. Calculate the angle $$\angle ABC$$.
A
$${\cos ^{ - 1}}\sqrt {{5 \over {11}}} $$
B
$${\cos ^{ - 1}}\sqrt {{6 \over {11}}} $$
C
$$\left( {90^\circ - {{\cos }^{ - 1}}\sqrt {{5 \over {11}}} } \right)$$
D
$$\left( {180^\circ - {{\cos }^{ - 1}}\sqrt {{5 \over {11}}} } \right)$$
2
WB JEE 2018
MCQ (Single Correct Answer)
+1
-0.25
Change Language
The velocity (v) of a particle (under a force F) depends on its distance (x) from the origin (with x > 0) $$v \propto {1 \over {\sqrt x }}$$. Find how the magnitude of the force (F) on the particle depends on x?
A
$$F \propto {1 \over {{x^{3/2}}}}$$
B
$$F \propto {1 \over x}$$
C
$$F \propto {1 \over {{x^2}}}$$
D
$$F \propto x$$
3
WB JEE 2018
MCQ (Single Correct Answer)
+1
-0.25
Change Language
The ratio of accelerations due to gravity g1 : g2 on the surfaces of two planets is 5 : 2 and the ratio of their respective average densities $${{\rho _1}}$$ : $${{\rho _2}}$$ is 2 : 1. What is the ratio of respective escape velocities v1 : v2 from the surface of the planets?
A
5 : 2
B
$${\sqrt 5 }$$ : $${\sqrt 2 }$$
C
5 : 2$${\sqrt 2 }$$
D
25 : 4
4
WB JEE 2018
MCQ (Single Correct Answer)
+1
-0.25
Change Language
A spherical liquid drop is placed on a horizontal plane. A small distance causes the volume of the drop to oscillate. The time period of oscillation (T) of the liquid drop depends on radius (r) of the drop, density ($$\rho $$) and surface tension (S) of th liquid. Which among the following will be a possible expression for T (where, k is a dimensionless constant)?
A
$$k\sqrt {{{\rho r} \over S}} $$
B
$$k\sqrt {{{{\rho ^2}r} \over S}} $$
C
$$k\sqrt {{{\rho {r^3}} \over S}} $$
D
$$k\sqrt {{{\rho {r^3}} \over {{S^2}}}} $$
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