A pickup truck has a box sitting loose in its bed. The box has a mass of 2.5 kg and the coefficient of static friction between the box and the pickup bed is 0.8. The mass of the truck is 3150 kg and its tires have a coefficient of static friction with the road of 0.9. The truck is currently going through a roundabout with a radius of 30m. How fast can the truck go and not have the box slide on the truck bed? Please answer in m/s.

On a mild saturday morning while people are working inside, the furnace keeps the temperature inside the building at 23degreesc. at noon the furnace is turned off, and the people go home. the temperature outside is a constant 16degreesc for the rest of the afternoon. if the time constant for the building is 3 hr, when will the temperature inside the building reach 18degreesc? if some windows are left open and the time constant drops to 2 hr, when will the temperature inside reach 18degreesc?