a body travels half journey with speed 10m/s and 1/3th journey with a speed of 5m/s. remaining distance with a speed of 2m/s. find the average speed.
Answers
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0
Explanation:
Let the total distance travelled be
′
d
′
. In the first part of journey, particle travels distance (d/2) with speed 5 m/s. So corresponding time, t
1
=
5
(d/2)
=
10
d
s.
Time of second and third part of journey is same, ⇒t
2
=t
3
Sum of distances of second and third parts is (d/2). Let the distance of second part of journey be
′
x
′
. Then,
6
x
=
4
(d/2)−x
[t
2
=t
3
]
⇒x=(3d/10)
t
2
=
6
x
=
10×6
3d
=(
20
d
)s=t
3
Total time of journey, t=t
1
+t
2
+t
3
⇒t=
10
d
+
20
d
+
20
d
=(
5
d
)s.
Average speed, V=
t
d
=
(d/5)
d
=5 m/s
Option (D) is the correct answer.
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