A man crosses a road 2.5 km wide in 750 seconds.
His speed is
Answers
Answer:
3.33 m/sec is the speed of a man
Answer:
Velocity of river (i.e., speed of river w.r.t. earth),
v
r/e
→
=2ms
−1
Velocity of boat w.r.t. river,
v
b/r
→
=4ms
−1
Width of river = 800m
Velocity of boat w.r.t. earth
v
b/e
→
=?
According to the given statement, the diagram will be as given in Fig.
a. When two vectors are acting at angle of 900, their resultant can be obtained by pythagorous theorem,
v
→
b/e
=
v
b/r
2
+v
r/e
2
=
16+4
=45ms
−1
To find direction, we have
tanθ=
v
b/r
v
r/e
=
4
2
=
2
1
⇒θ=tan
−1
(
2
1
)
b. Time taken to cross the river is
Velocityofboatw.r.triver
Displacement
Velocity of boat w.r.t. river is used since it is the velocity with which the river is crossed.
So the boat will cross in
4
800
=200s
c. The desired position on other side is A, but due to the current of river, boat is drifted to position B. To find out this drift, we need time taken in all to cross the river (200 s) and speed of current (2ms
−1
).
So the distance AB = Time taken × Speed of current
=200×2=400m
Hence, the boat is drifted by 400 m away from position A.
Step-by-step explanation:
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