is spring constant the ratio of external force to displacement from mean position or the ratio of restoring force to displacement from mean position?​

Ingrid wrote the hypothesis below. if the temperature of a liquid increases, the density of the liquid decreases because the particles move farther apart. what are the variables in her hypothesis?

Explain the comparisons between nature and packingtown that appears on pages 81 and 82 answer

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.