Flagging on an expressway: O A. should not be done at night.
O B. is best done in the summer.
O C. is particularly dangerous.
O D. is just as dangerous as flagging on any other road.

Coiled springs ought to be very strong and stiff. si3n4 is a strong, stiff material. would you select this material for a spring? explain.

The short distance from the objective lens to the object causes problems at high magnification. which of the following is the most serious? a. cleaning the object surface b. positioning the object c. reflection from the object surface. d. illumination of the object

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 the air is well mixed within the room, and an equal mass flow of air at room temperature (changing with time) is withdrawn through a return duct.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.