What would be the wavelength of the 21-cm-line if it was coming from a distance of 8,000,000,000 (8*10^9) light-years

When a 5.0kg cart undergoes a 2.2m/s increase in speed, what is the impulse of the cart

Using a wheel and axle, a farmer is trying to lift a bucket of water from the bottom of a well. the larger wheel has a radius of 40 cm compared to the axle that has a radius of 10 cm. if a bucket of water is 50 n, then how much effort is required to raise it? 12.5 n 200 n 2 n 500 n

How does the entropy of steam compare to the entropy of ice?