A low-frills patio or deck is pretty cheap. Everyone's definition of cheap is different, but decks can be had for as low as $1,000, according to Jessica Piha, a spokeswoman for Porch.com, a website that helps homeowners find the right contractor. But the average deck costs $8,300, Piha says. And how much is a cheap patio? The cost to install a 200-square-foot concrete patio is about $740 to $840 on average, according to HomeWyse.com, an online reference for home projects. But here's why you probably won't buy a cheap patio. If you're pining over someone's patio, you presumably don't want a concrete slab.
The acceleration due to gravity on the surface of the Moon. The mass of the Moon is 7.35 x 10^22 kg and the average radius of the Moon is 1.74 x 10^6 m. Plugging into the formula, we have: g = (6.67 x 10^-11 N-m^2/kg^2)(7.35 x 10^22 kg )/(1.74 x 10^6 m)^2 = (4.9 x 10^12 )/(3.03 x 10^12) = 1.6 m/s^2.
Other factors affecting rotational speed include the rapidity of a planet's initial formation (faster collapse means more angular momentum conserved) and impacts from meteorites, which can slow down a planet or knock it off stride. Earth's rotation, he adds, is also affected by the tidal pull of the Moon. Because of the Moon, the spin of the Earth is slowing down at a rate of about 1 millisecond per year. The Earth spun around at a faster clip in the past, enough so that during the time of the dinosaurs a day was about 22 hours long. In addition to slowing the Earth's rotation, the Moon's tidal pull is causing the Moon to slowly recede from the Earth, at a rate of about 1 millimeter per year.