Question
The angle of elevation of an aeroplane from a point on
the ground is 60°. After 12 seconds flight the elevation changes to 30°, if the aeroplane is flying at a height of 1200√3 m. find the speed of the aeroplane.Solution
Distance between two place in which angle change is D = n(cotθ₁ + cotθ₂) Distance = 1200√3 (cot30° + cot60°) = 1200√3 × √3 - 1/√3 = 1200√3 ×2/√3 = 2400 m So, distance covered by plane in 12 sec = 2400 m Speed of plane = 2400/12 = 200 m/sec.
The speed of a boat in still water is 5 km/hr more than that of the current. The time taken by the boat to cover 425 km downstream is 8.5 hours. Find th...
A man can row 25/2 km an hour in still water and he finds that it takes him thrice as long as long to row down the river. The rate of stream is:
The boat's speed in still water is 20% greater than the speed of the stream. If it takes the boat 4 hours more to travel 176 km d...
The speed of a boat in still water is 7 km/hr and speed of current is 4 km/hr. If time taken to cover a certain distance upstream is 22 hours, then how ...
The speed of a boat in still water is 22 km/h and the speed of the stream is 8 km/h. The boat first goes 60 km downstream and then travels upstream a di...
A man can row at a speed of 64 km/h in still water to a certain upstream point and back to the starting point in a river which flows at 8 km/h. Find his...
Ratio of speed of boat in downstream and speed of stream is 9:4, if speed of current is 8 km/hr, then find distance travelled (in km) upstream in 5 hours.
The speed of current is 26 km/hr. If the speed of the boat in still water had been 12 km/hr more than the original speed then it would take 7.5 hours to...
The speed of a boat is that of the current of water is 30:7. The boat goes along with the current in 4 hours 12 minutes. It will come back in
Find the total distance covered by boat in each upstream and downstream in 4 hours if the speed of boat in still water and speed of current is 15 km/h a...
Relevant for Exams:
