Bullet of mass embeds itself in a

wooden block with mass which then compresses a spring by a distance

before coming to rest. the coefficient of kinetic friction

between the block and table is (a) what is the

initial velocity (assumed horizontal) of the bullet? (b) what

fraction of the bullet’s initial kinetic energy is dissipated

(in damage to the wooden block, rising temperature, etc.)

in the collision between the bullet and the block?

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?