1
JEE Main 2021 (Online) 27th August Evening Shift
MCQ (Single Correct Answer)
+4
-1
The boxes of masse 2 kg and 8 kg are connected by a massless string passing over smooth pulleys. Calculate the time taken by box of mass 8 kg to strike the ground starting from rest. (use g = 10 m/s2)

A
0.34 s
B
0.2 s
C
0.25 s
D
0.4 s
2
JEE Main 2021 (Online) 26th August Morning Shift
MCQ (Single Correct Answer)
+4
-1
The initial mass of a rocket is 1000 kg. Calculate at what rate the fuel should be burnt so that the rocket is given an acceleration of 20 ms-2. The gases come out at a relative speed of 500 ms$$-$$1 with respect to the rocket : [Use g = 10 m/s2]
A
6.0 $$\times$$ 102 kg s$$-$$1
B
500 kg s$$-$$1
C
10 kg s$$-$$1
D
60 kg s$$-$$1
3
JEE Main 2021 (Online) 27th July Evening Shift
MCQ (Single Correct Answer)
+4
-1
A particle of mass M originally at rest is subjected to a force whose direction is constant but magnitude varies with time according to the relation

$$F = {F_0}\left[ {1 - {{\left( {{{t - T} \over T}} \right)}^2}} \right]$$

Where F0 and T are constants. The force acts only for the time interval 2T. The velocity v of the particle after time 2T is :
A
2F0T/M
B
F0T/2M
C
4F0T/3M
D
F0T/3M
4
JEE Main 2021 (Online) 25th July Evening Shift
MCQ (Single Correct Answer)
+4
-1
A force $$\overrightarrow F = (40\widehat i + 10\widehat j)N$$ acts on a body of mass 5 kg. If the body starts from rest, its position vector $$\overrightarrow r$$ at time t = 10 s, will be :
A
$$(100\widehat i + 400\widehat j)m$$
B
$$(100\widehat i + 100\widehat j)m$$
C
$$(400\widehat i + 100\widehat j)m$$
D
$$(400\widehat i + 400\widehat j)m$$
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