Difference between gravitational field strength vs gravitational pull?

What produces light and all other electromagnetic waves? a) the photoelectric phenomena b) heated metals c) charged particles d) radioactive samples (pls explain if you can : )

What equation is used to calculate the weight of an object on a plant ?

An ideal otto cycle has a compression ratio of 8. at the beginning of the compression process, air is at 95 kpa and 27°c, and 750 kj/kg of heat is transferred to air during the constant-volume heat-addition process. assuming constant specific heats at room temperature, determine (a) the pressure and temperature at the end of the heat-addition process, (b) the net work output, (c) the thermal efficiency, and (d) the mean effective pressure for the cycle. (4390 kpa, 1730 k; 423 kj/kg; 56.4%; 534 kpa)