What is more dense: 2 g/ml or 3 g/ml ?

Which instrument is used to measure air temperature

Awave is produced in a rope. the wave has a speed of 33 m/s and a frequency of 22 hz.

Consider a 1000 w iron whose base plate is made of 0.5 cm thick aluminum alloy 2024-t6 (ρ = 2770 kg/m3 and cp = 875 j/kg°c). the base plate has a surface area of 0.03 m2. initially, the iron is in thermal equilibrium with the ambient air at 22°c. assuming 90% of the heat generated in the resistance wires is transferred to the plate, determine the minimum time needed for the plate temperature to reach 200°c.