5. Billy is trying to slide an 80 kg box of equipment across the floor. The coefficient of static friction between the box and the floor is 0.55. A) If Billy only pushes horizontally against the box, how much force must he push with to initiate movement of the box? B) Billy then decides to pull the box instead at an angle of 25o. How much force must he produce to move the box by pulling it an angle compared to pushing it?

Determine the net charge of the predominant form of arg at (a) ph 1.0, (b) ph 5.0, (c) ph 10.5, and (d) ph 13.5

If frequency goes up, what happens to wavelength? does it get shorter or longer?

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?