Explain why grain boundaries can act as barriers to dislo cation motion 29. state the difference between grain boundaries effect and grain size effect on strength of metals 30. the grain refinement effect on the strength can be described through the hall-petch equation explain and show why this equation is not valid in the nona-sized grains (< 50 nm)

A30 kg weight lies on top of a massless piston of area a = 0.01 m2 the exterior air is at a (constant) p =1 atm and t = 27 c. the interior gas is 0.4 moles of (ideal) n2 and it has initial temperature 27.00 degrees c. 1. what is the initial pressure in the interior? a. 29.4 kpa b. 130.7 kpa c. 101.3 kpa the next three questions concern what happens when an amount of heat q is slowly added to the interior, raising the piston by 1 mm and raising the interior temperature to 27.40 c

Using the free-body diagram, calculate the net force acting on the sled. is the sled in a state of dynamic equilibrium?

Describe how the motion of a spring being pushed forward and backward is similar to the motion of air particles in a sound wave.