-
A hydrogen-filled balloon ascending at the rate of 18 kmph was drifted by wind. Its angle of elevation at 10th and 15th minutes were found to be 60° and 45° respectively. The wind speed (in whole numbers) during the last five minutes, approximately, is equal to
-
- 7 km./hr.
- 11 km./hr.
- 26 km./hr.
- 33 km./hr.
Correct Option: D
If height of balloon = 3800 √3 m, then.
| tan 60° = | AB |
| ⇒ √3 = | AB |
⇒ AB = 3800 m
| tan 45° = | AC |
| ⇒ 1 = | AC |
⇒ AC = 3800 √3 m
∴ PQ = AC – AB
= (3800 √3 – 3800)
= 3800 × 0.732 = 3800 ( √3 –1)
= 2782 m
&thete4; Required speed
| = |  |  | km/hr. | (5/60) × 1000 |
= 33.3 km/hr. (Approximately)
