A 3 kg mass is held against spring compressed horizontally by 0.5 m. If the spring constant is 145 N/m how much energy is stored in the spring? What is the velocity of the mass when pushed by the spring? How far will the mass slide on the surface if the coefficient of kinetic friction on the surface is 0.25?

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.