1
JEE Main 2021 (Online) 16th March Evening Shift
MCQ (Single Correct Answer)
+4
-1
Out of Syllabus
Change Language
Two identical antennas mounted on identical towers are separated from each other by a distance of 45 km. What should nearly be the minimum height of receiving antenna to receive the signals in line of sight? (Assume radius of earth is 6400 km)
A
158.2 m
B
79.1 m
C
19.77 m
D
39.55 m
2
JEE Main 2021 (Online) 16th March Evening Shift
MCQ (Single Correct Answer)
+4
-1
Change Language
A large block of wood of mass M = 5.99 kg is hanging from two long massless cords. A bullet of mass m = 10 g is fired into the block and gets embedded in it. The (block + bullet) then swing upwards, their centre of mass rising a vertical distance h = 9.8 cm before the (block + bullet) pendulum comes momentarily to rest at the end of its arc. The speed of the bullet just before collision is :
(take g = 9.8 ms-2)

JEE Main 2021 (Online) 16th March Evening Shift Physics - Center of Mass and Collision Question 49 English
A
831.4 m/s
B
811.4 m/s
C
841.4 m/s
D
821.4 m/s
3
JEE Main 2021 (Online) 16th March Evening Shift
MCQ (Single Correct Answer)
+4
-1
Out of Syllabus
Change Language
Calculate the time interval between 33% decay and 67% decay if half-life of a substance is 20 minutes.
A
40 minutes
B
60 minutes
C
13 minutes
D
20 minutes
4
JEE Main 2021 (Online) 16th March Evening Shift
MCQ (Single Correct Answer)
+4
-1
Change Language
A mosquito is moving with a velocity $$\overrightarrow v = 0.5{t^2}\widehat i + 3t\widehat j + 9\widehat k$$ m/s and accelerating in uniform conditions. What will be the direction of mosquito after 2 s?
A
$${\tan ^{ - 1}}\left( {{\sqrt {85} } \over 6}\right)$$ from y-axis
B
$${\tan ^{ - 1}}\left( {{5 \over 2}} \right)$$ from y-axis
C
$${\tan ^{ - 1}}\left( {{2 \over 3}} \right)$$ from x-axis
D
$${\tan ^{ - 1}}\left( {{5 \over 2}} \right)$$ from x-axis
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