Home
Class 12
MATHS
A bird is sitting on the top of a vertic...

A bird is sitting on the top of a vertical pole 20 m high and its elevation from a point O on the ground is `45o` . It flies off horizontally straight away from the point O. After one second, the elevation of the bird from O is reduced to `30o` . Then the speed (in m/s) of the bird is (1) `40(sqrt(2)-1)` (2) `40(sqrt(3)-2)` (3) `20""sqrt(2)` (4) `20(sqrt(3)-1)`

A

`40 (sqrt(2)-1)`

B

`40 sqrt((3)-sqrt(2))`

C

`20 sqrt(2)`

D

`20(sqrt(3)-1)`

Text Solution

Verified by Experts

(4) `tan 30 ^2 =(20)/(20 + x )= 1/sqrt(3)`
`rArr 20 + x = 20 sqrt( 3)`
`rArr x= 20 ( sqrt( 3 -1) `
`Speed is 20 (sqrt(3-1)m//sec)`.
Doubtnut Promotions Banner Mobile Dark
|

Topper's Solved these Questions

  • HIGHT AND DISTANCE

    CENGAGE ENGLISH|Exercise Exercises|18 Videos
  • GRAPHS OF TRIGONOMETRIC FUNCTIONS

    CENGAGE ENGLISH|Exercise Exercises|22 Videos
  • HYPERBOLA

    CENGAGE ENGLISH|Exercise COMPREHENSION TYPE|2 Videos

Similar Questions

Explore conceptually related problems

A snake observes an eagle perching on the top of a pole 20 m high. Its elevation from snake s eye is 45^@ before it hies off horizontally straight away from the snake and after one second the elevation of the eagle reduces to 30^@ .The speed of the eagle is

A bird is sitting on the top of an 80 m high tree. From a point on the ground, the angle of elevation of the bird is 45^(@) . The bird flies away horizontally in such a way that it remained at a constant height from the ground. After 2 seconds, the angle of elevation of the bird from the same point is 30^(@) . Find the speed of flying of the bird. (Take sqrt3=1.732 ).

AB is a vertical pole with B at the ground level and A at the top. A man finds that the angle of elevation of the point A from a certain point C on the ground is 60o . He moves away from the pole along the line BC to a point D such that C D""=""7""m . From D the angle of elevation of the point A is 45o . Then the height of the pole is (1) (7sqrt(3))/2 1/(sqrt(3)-1)m (2) (7sqrt(3))/2 sqrt(3)+1m (3) (7sqrt(3))/2 sqrt(3)-1m (4) (7sqrt(3))/2 sqrt(3)+1m

A pole 6 m high casts a shadow 2 sqrt 3 m long on the ground, then find the angle of elevation of the sun.

The angle of elevation of the top of a vertical tower P Q from a point X on the ground is 60o . At a point Y , 40m vertically above X , the angle of elevation of the top is 45o . Calculate the height of the tower.

The angle of elevation of the top of a vertical tower P Q from a point X on the ground is 60o . At a point Y , 40m vertically above X , the angle of elevation of the top is 45o . Calculate the height of the tower.

A statue, 1.6 m tall, stands on the top of a pedestal. From a point on the ground, the angle of elevation of the top of the statue is 60o and from the same point the angle of elevation of the top of the pedestal is 45o . Find the height of pedestal

An aeroplane flying horizontally 1 km above the ground is observed at an elevation of 60o . After 10 seconds, its elevation is observed to be 30o . Find the speed of the aeroplane in km/hr.

It is found that on walking x metres towards a chimney in a horizontal line through its base, the elevation of its top changes from 30o to 60o . The height of the chimney is 3sqrt(2)x (b) 2sqrt(3)x (c) (sqrt(3))/2x (d) 2/(sqrt(3))x

A statue, 1.6 m tall, stands on the top of a pedestal. From a point on the ground, the angle of elevation of the top of the statue is 60^o and from the same point the angle of elevation of the top of the pedestal is 45^o . Find the height of the pedestal.