Why are the nuclei of the heavier elements radioactive and not the lighter elements nuclei?

If the ama of the inclined plane below is 2, calculate the ima and efficiency. ima = efficiency =

An ionic compound can conduct electricity when a it is dissolved in water b its crystals are ground into powder c it is in solid form d it is heated to just below its melting point

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.