47.
A motor boat is to reach at a point 30° upstream (w.r.t normal) on other side of a river flow,
velocity 5 m/s. Velocity of motorboat w.r.t. water is 5v3 m/s. The driver should steer the be
angle
1) 120°w.r.t stream direction
2) 30° w.r.t normal to the bank
3) 30°w.r.t the line of destination from starting point.
4) None of these
observes that the rain is falling vertically downward. When he starts runni
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1
Answer:
Kinematics
V
mw
= relative velocity of boat with respect to water
v
ˉ
m=−(5
3
cosθ)i+5
3
cos30j+5i
taking
i
direction parallel to river flow and
j
direction
l
lar
to river flow
v
^
m
=−7.5i+
2
5
3
j+5
i
^
v
^
m
=−2.5i+
2
5
3
j
=tan
−1
[
2×2.5
−5
3
]
=tan
−1
(−
3
)
=120
o
stream direction
velocity of boat
v
m
=v
mw
+v
w
solution
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