Your forehead can withstand a force of about 6.0 kn before fracturing, while your cheekbone can only withstand about 1.3 kn. a. if a 140 g baseball strikes your head at 30 m/s and stops in 0.0015 s, what is the magnitude of the ball's acceleration? b. what is the magnitude of the force that stops the baseball? c. what force does the baseball apply to your head? explain. d. are you in danger of a fracture if the ball hits you in the forehead? in the cheek?

Aparticle of mass m is placed in a one-dimensional box of length l. the box is so small that the particle’s motion is relativistic, so that e p2/2m is not valid. (a) derive an expression for the energy levels of the particle using the relativistic energy–momentum relation and the quantization of momentum that derives from connement. (b) if the particle is an electron in a box of length l 1.00 1012 m, nd its lowest possible kinetic energy. by what percent is the nonrelativistic formula for the energy in error?

Asteel tube (k=50 w/mk) of inner and outer diameter di = 20mm and do=26mm, respectively, is used to transfer heat from hot gases flowing over the tube (h-hot = 200w/m2k) to cold water flowing through the tube (h-cold = 8000 w/m2k). what is the cold-side overall heat transfer coefficient uc? to enhance heat transfer 16 straight fins of rectangular profile are installed longitudinally along the outer surface of the tube. the fins are equally spaced around the circumference of the tube, each having a thickness of 2mm and a length of 15mm. what is the corresponding overall heat transfer coefficient uc? *solve for uc in both cases*

Dc versus ac problem. suppose your dc power supply is set to 15 v and the vertical setting on the oscilloscope is at 5 v/div. how many divisions will the trace deflect if you connect the output of the power supply to the scope with the a input switch set on dc? how many divisions if the switch is on ac?