1
JEE Main 2019 (Online) 9th April Evening Slot
+4
-1
The position of a particle as a function of time t, is given by
x(t) = at + bt2 – ct3
where a, b and c are constants. When the particle attains zero acceleration, then its velocity will be :
A
$$a + {{{b^2}} \over {c}}$$
B
$$a + {{{b^2}} \over {4c}}$$
C
$$a + {{{b^2}} \over {3c}}$$
D
$$a + {{{b^2}} \over {2c}}$$
2
JEE Main 2019 (Online) 9th April Evening Slot
+4
-1
The position vector of a particle changes with time according to the relation $$\overrightarrow r (t) = 15{t^2}\widehat i + (4 - 20{t^2})\widehat j$$
What is the magnitude of the acceleration at t = 1 ?
A
50
B
25
C
40
D
100
3
JEE Main 2019 (Online) 9th April Morning Slot
+4
-1
The stream of a river is flowing with a speed of 2km/h. A swimmer can swim at a speed of 4km/h. What should be the direction of the swimmer with respect to the flow of the river to cross the river straight ?
A
150°
B
120°
C
60°
D
90°
4
JEE Main 2019 (Online) 8th April Evening Slot
+4
-1
A particle starts from origin O from rest and moves with a uniform acceleration along the positive x-axis. Identify all figures that correctly represent the motion qualitatively. (a = acceleration, v = velocity, x = displacement, t = time)
A
(B), (C)
B
(A)
C
(A), (B), (C)
D
(A), (B), (D)
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