1
WB JEE 2017
MCQ (Single Correct Answer)
+1
-0.25
Change Language
Three vectors $$\overrightarrow A $$ = a$$\widehat i$$ + $$\widehat j$$ + $$\widehat k$$; $$\overrightarrow B $$ = $$\widehat i$$ + b$$\widehat j$$ + $$\widehat k$$ and $$\overrightarrow C $$ = $$\widehat i$$ + $$\widehat j$$ + c$$\widehat k$$ are mutually perpendicular ($$\widehat i$$, $$\widehat j$$ and k are unit vectors along X, Y and Z-axes respectively). The respective values of a, b and c are
A
0, 0, 0
B
$$ - {1 \over 2}$$, $$ - {1 \over 2}$$, $$ - {1 \over 2}$$
C
1, $$-$$1, 1
D
$${1 \over 2}$$, $${1 \over 2}$$, $${1 \over 2}$$
2
WB JEE 2017
MCQ (Single Correct Answer)
+1
-0.25
Change Language
A block of mass 1 kg starts from rest at x = 0 and moves along the X-axis under the action of a force F = kt, where t is time and k = 1 Ns$$-$$1. The distance the block will travel in 6 seconds is
A
36 m
B
72 m
C
108 m
D
18 m
3
WB JEE 2017
MCQ (Single Correct Answer)
+2
-0.5
Change Language
A particle with charge Q coulomb, tied at the end of an inextensible string of length R metre, revolves in a vertical plane. At the centre of the circular trajectory, there is a fixed charge of magnitude Q coulomb. The mass of the moving charge M is such that $$Mg = {{{Q^2}} \over {4\pi {\varepsilon _0}{R^2}}}$$. If at the highest position of the particle, the tension of the string just vanishes, the horizontal velocity at the lowest point has to be
A
0
B
$$2\sqrt {gR} $$
C
$$\sqrt {2gR} $$
D
$$\sqrt {5gR} $$
4
WB JEE 2017
MCQ (Single Correct Answer)
+2
-0.5
Change Language
A bullet of mass 4.2 $$ \times $$ 10$$-$$2 kg, moving at a speed of 300 ms$$-$$1, gets stuck into a block with a mass 9 times that of the bullet. If the block is free to move without any kind of friction, the heat generated in the process will be
A
45 cal
B
405 cal
C
450 cal
D
1701 cal
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