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Question
Physics
The position vector of a particle changes with time according to the relation vecr (t) = 15t2 hati + ( 4 -20 t2) hatj. What is the magnitude of the acceleration at t = 1 ?
Q. The position vector of a particle changes with time according to the relation
r
(
t
)
=
15
t
2
i
^
+
(
4
−
20
t
2
)
j
^
. What is the magnitude of the acceleration at
t
=
1
?
4420
203
JEE Main
JEE Main 2019
Motion in a Plane
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A
40
6%
B
100
10%
C
25
12%
D
50
71%
Solution:
r
=
15
t
2
i
^
+
(
4
−
20
t
2
)
j
^
v
=
d
t
d
r
=
30
t
i
^
+
(
−
40
t
)
j
^
a
=
d
t
d
v
=
30
i
^
−
40
j
^
∣
a
∣
=
50
m
/
s
2