Arock falls off a cliff and falls for 3 secs. how high was the cliff?

Which units can be used to measure length or distance? check all that apply. gram meter kilometer liter inch

Which is the correct symbol for an isotope of iodine with 53 protons and 78 neutrons?

Engineers find a new metal that is stronger than steel but much lighter. this material is also significantly cheaper than what is currently used for most aircraft, available in large quantities, and easy to manufacture. the engineers are excited because this new material will lower the costs of buying and operating airplanes for companies. what is probably the best step for the engineers to make next?