In a test experiment pn a model aeroplane in a wind tunnel, the flow speeds on the upper and lower surfaces of the wing are `70 m s^-1` and `63 m s^-1` respectively. What is the lift on the wing if its area is `2.5 m^2` ? Take the density of air to be `1.3 kg m^-3`.

A sound wave travels at a speed of 339 m s^-1 . If its wavelength is 1.5 cm, what is the frequency of the wave? Will it be audible?

The ratio of the edges of a cuboid is 1:2:3 and its volume is 1,296 cm^3 . What is the area of the whole surface?

A plane is in level flight at constant speed and each of its two wings has an area of 25 m^2 . If the speed of the air is 180 km/h over the lower wing and 234 km/h over the upper wing surface, determine the plane’s mass. (Take air density to be 1 kg m^-3) .

Rain is falling vertically with a speed of 30 m s^-1 . A woman rides a bicycle with a speed of 10 m s^-1 in the north to south direction. What is the direction in which she should hold her umbrella?

Find the frequency of revolution of an electron in Bohr's 2nd orbit; if the radius and speed of electron in that orbit is 2.14×10^(−10) m and 1.09×10^6m/s respectively.

A 10 kg weight is accelerated from rest to 20 m/s in 1 sec. What force acts on it:

The blades of a windmill sweep out a circle of area A. (a) If the wind flows at a velocity v perpendicular to the circle, what is the mass of the air passing through it in time f?(b) What is the kinetic energy of the air? (c) Assume that the windmill converts 25% of the wind’s energy into electrical energy, and that A = 30 m^- 2 , v = 36 km/h and the density of air is 1.2 kg m^-3 . What is the electrical power produced?

If m, v and c respectively denote mass, speed and the velocity of light, then in the equation m = m_0(1-v^2/c^2)^(-1/2), find the dimension of m_0

A man’stationed between two hills fires a gun. He hears the first echo after 1 s and the second after 2 s. What is the distance between the hills. The speed of sound in air is 330 m/s.

A stream of water flowing horizontally with a speed of 15 m s^1 gushes out of a tube of cross-sectional area 10^2 m2, and hits a vertical wall nearby. What is the force exerted on the wall by the impact of water, assuming it does not rebound?