Select all the statements that are always true about periodic waves: The speed of the particles constituting a periodic wave is constant. The speed that a periodic wave propagates is constant. Particles that constitute the wave always move in the same direction that the wave travels. Waves carry energy, but not particles, through a medium. All waves travel at the speed of light.

The answer is 30 but I don't know how it arrived at that answer! Please explain

..................... The dimensions of the quantity kinetic energy, designated by K, are kg m/s, It can be written in terms of the momentum p and mass m as K = 2m (a) What are the units of momentum in terms of fundamental SI units? (Use the following as necessary: kg, m, and s.) [P) - (b) Force is measure in units of newtons, N, where 1N- 1 kg m/s. What are the units of momentum p in terms of a newton and another fundamental SI unit? (Use the. following as necessary: N, m, and s.) [P) = (c) What If? Physicists often measure the momentum of subatomic particles moving near the speed of light in units of MeV/c, where c is the speed of light, and 1 Mev = 1.6 x 101 kg m/s. Based on this, what are the units of momentum for a high-speed subatomic particle in terms of fundamental SI units? What are the units of momentum for a high-speed subatomic particle in terms of a newton and another fundamental SI unit? [P] -

In one of the videos I said that a typical American household uses energy at a rate of about 10,000 joules per second.  A shorthand unit for this would be "10 kilowatts".  Using energy at this rate costs about $1.50 per hour (this is not quite right, as it assumes that all the energy is electrical energy, which is relatively cheap, but let's go with this for an estimate).  How much does this energy usage cost for a year?