A particle of mass 1 kg is hanging from a spring of force constant 100 Nm^$$-$$1. The mass is pulled slightly downward and released so that it executes free simple harmonic motion with time period T. The time when the kinetic energy and potential energy of the system will become equal, is $${T \over x}$$. The value of x is _____________.

If the sum of the heights of transmitting and receiving antennas in the line of sight of communication is fixed at 160 m, then the maximum range of LOS communication is ___________ km. (Take radius of Earth = 6400 km)

A square shaped wire with resistance of each side 3$$\Omega$$ is bent to form a complete circle. The resistance between two diametrically opposite points of the circle in unit of $$\Omega$$ will be ___________.

A wire having a linear mass density 9.0 $$\times$$ 10^$$-$$4 kg/m is stretched between two rigid supports with a tension of 900 N. The wire resonates at a frequency of 500 Hz. The next higher frequency at which the same wire resonates is 550 Hz. The length of the wire is ____________ m.