a accident investigor estimates that a vehicle hit a bridge abutment at a speed of 20miles/hour based on his assessment of the damage. leading to the accident location he observed skid marks of 100 feet on the pavement (F=0.35)and 75feet on the grass shoulder (F=0.25)there is no grade. estimate the speed of the vehicle at the beginning of the sikd marks?

To save energy, the air supply to a 2000 ft office has been shut off overnight and the room temperature has dropped to 40°f. in the morning, the thermostat is reset to 70°f and warm air at 120 f begins to flov in at 200ft'/min. the air is well mixed within the room, and an equal mass flow of air at room temperature (changing with time) is withdrawn through a return duct. the air pressure is nearly 1 atm everywhere. ignoring heat transfer with the surroundings and kinetic and potential energy effects, estimate how long it takes for the room temperature to reach 70°f. plot the room temperature as a function of time.