Isotope A is radioactive and decays to isotope B which is also radioactive and decays to C. Isotope C is stable. The half life of A is 1.0 days. The half life of B is 2.0 days. Assume that at time zero there were 1000 atoms of A, zero atoms of B and zero atoms of C. After 4.0 days:.
a. How many atoms of A remain and what is the activity of A?
b. How many atoms of B exist and what is the activity of B?
Refer to Section 2.9, Radioactivity Calculations

Apump is used to circulate hot water in a home heating system. water enters the well-insulated pump operating at steady state at a rate of 0.42 gal/min. the inlet pressure and temperature are 14.7 lbf/in.2, and 180°f, respectively; at the exit the pressure is 60 lbf/in.2 the pump requires 1/15 hp of power input. water can be modeled as an incompressible substance with constant density of 60.58 lb/ft3 and constant specific heat of 1 btu/lb or. neglecting kinetic and potential energy effects, determine the temperature change, in °r, as the water flows through the pump.

Acompressor receives the shaft work to decrease the pressure of the fluid. a)- true b)- false

Abrake has a normal braking torque of 2.8 kip in and heat-dissipating cast-iron surfaces whose mass is 40 lbm. suppose a load is brought to rest in 8.0 s from an initial angular speed of 1600 rev/min using the normal braking torque; estimate the temperature rise of the heat dissipating surfaces.