An aircraft is flying at a height of 3400 m above the ground. If the angle subtended at a ground observation point by the aircraft positions `10.0 s apart is 30^@ what is the speed of the aircraft?

A man holds a 10 kg box 2m above the ground.What is the work done?

A kite is flying at a height of 60 m above the ground.The string attached to the kite is temporarily tied to a point on the ground.The inclination of the string with the ground is 60^@ .Find the length of the string,assuming that there is no slack in the string.

An aeroplane flying horizontally at a height of 1.5 km above the ground is observed at a certain point on the earth to subtend an angle 60°. After 15 second its angle of elevation is observed to be 30°. Calculate the speed of aeroplane in Km/h.

A 1.2m tall girl spots a balloon moving with the wind in a horizontal line at a height of 88.2 m from the ground.The angle of elevation of the balloon from the eyes of the girl at any instant is 60^@ .After some time,the angle of elevation reduces to 30^@ (see Fig 9.13),Find the distance travelled by the balloon during the interval..

If the top of a temple subtends an angle of 30^@ at a point on the ground 300m away from its base,find the height of the temple.

If the top of a temple subtends an angle of 60^@ at a point on the ground 400m away from its base,find the height of the temple.

A rain drop of radius 2 mm falls from a height of 500 m above the ground. It falls with decreasing acceleration (due to viscous resistance of the air) until at half its original height, it attains its maximum (terminal) speed, and moves with uniform speed thereafter. What is the work done by the gravitational force on the drop in the first and second half of its journey? What is the work done by the resistive force in the entire journey if its speed on reaching the ground is 10 m s-^1 ?

A satellite orbits the earth at a height of 400 km above the surface. How much energy must be expended to rocket the satellite out of the earth’s gravitational influence? Mass of the satellite = 200 kg, mass of the earth = 6.0 xx10^24 kg, radius of the earth = 6.4 xx10^6 m, G = 6.67 x 10^-11 N m^2 kg ^-2 .

An aeroplane when flying at a height of 3125mfrom the ground passes vertically below another plane at an instant when the angles of elevation of the two planes from the same point on the ground are 30° and 60° respectively. Find the distance between the two planes at the instant.

A vertical post of height 5sqrt3 m above the horizontal ground casts a shadow of length 15 m on the ground.Find the angle of elevation of the sun.