Why do you think a compass needle always points north? (Write your initial ideas. It is OK if you are unsure about them.)

Determine the amount of work done when a crane lifts a 100-n block form 2m above the ground to 6m above the ground

The force needed to overcome static friction is usually less than that needed to overcome kinetic friction.true or false?

Athin electrical heater is inserted between a long circular rod and a concentric tube with inner and outer radii of 20 and 40 mm. the rod (a) has a thermal conductivity of ka = 0.15 w/(m*k), while the tube (b) has a thermal conductivity of kb = 0.8 w/(m*k) and its outer surface is subjected to convection with a fluid of temperature t= -15°c and heat transfer coefficient 60 w/(m2 *k). the thermal contact resistance between the cylinder surfaces and the heater is negligible. (a) determine the electrical power per unit length of the cylinders (w/m) that is required to maintain the outer surface of cylinder b at 15°c. (b) what is the temperature at the center of cylinder a?