An Aeroplan flying horizontally at a height of 3 km. Above the ground is observed at a certain point on earth to subtend an angle of 60 °. After 15 sec flight, its angle of elevation is changed to 30 °. The speed of the Aeroplan (taking √3 = 1.732) 

An observer on the top of a mountain, 500 m above the sea level, observes the angles of depression of the two boats in his same place vision to be 45 ° and 30 ° respectively. Then the distance between the boats, if the boats are on the same side of the mountain, is 

A straight tree breaks due to storm and the broken part bends so that the top of the tree touches the ground making an angle of 30 ° with the ground. The distance from the foot of the tree to the point, where the top touches the ground is 10m. Find the total height of the tree 

129 meter from the foot of a cliff on level of ground, the angle of elevation of the top of cliff is 30 °. The height of this cliff is 

A person from the top of a hill observes a vehicle moving towards him at a uniform speed. It takes 10 minutes for the angle of depression to change from 45 ° to 60 °. After this the time required by the vehicle to reach the bottom of the hill is 

The angles of elevation of top and bottom of flag kept on a flag post from 30 metres distance, are 45 ° and 30 ° respectively. Height of the flag is [ taking 13 = 1.732) 

The shadow of a tower when the angle of elevation of the sun is 45 °, is found to be 10 m longer that when it was 60 °. The height of the tower is 

A telegraph post is bent at a point above the ground. Its top just touches the ground at a distance of 8√3 m from its feet and makes an angle of 30 ° with the horizontal. The height (in metre) of the post is