What is the frequency of a wave that has a period of 50 seconds

You've already seen the value of 9.8 in this lesson. what's this value called? what quantity does it represent?

Ihave a density of 1.61g/cm^3 and a mass of 28g. find the missing value

An ideal otto cycle has a compression ratio of 10.5, takes in air at 90 kpa and 40°c, and is repeated 2500 times per minute. using constant specific heats at room temperature, determine the thermal efficiency of this cycle and the rate of heat input if the cycle is to produce 90 kw of power.