A machine is supplied energy at a rate of 4,000 W and does useful work at a rate of 3,760 W. What is the efficiency of the machine? a. 92 percent b. 94 percent c. 96 percent d. 97 percent?
A car with a mass of 2,000. kilograms is moving around a circular curve at a uniform velocity of 25 meters per second. The curve has a radius of 80 meters. What is the centripetal force on the car? a. 625 N b. 703N c. 15,625 N d. 20,250 N
A compacted body of iron powder is sintered into a 20mm-diameter, 45-mm-tall cylinder which, upon weighing, is found to have a mass of 98g. Calculate the apparent density, the percentage of theoretical density, and the void volume (porosity) in percent.
Liquid H2O at 8 MPa and 40 degrees C is heated reversibly at constant pressure until the temperature reaches 600 degrees C. Determine the change in entropy of the surrounding (universe).
A bar of steel 1 by 1½ in cross section and 6 in long is subjected to a pull of 6000 lb. What is the average tensile stress in the bar?
Large stationary brayton cycly gas turbine power plant delivers a powr output of 100MW to an electric generator . Minimum temperature is 300K so T1= 300k max temp is 1600k so T3= 1600k Minimum pressure in the cycle is 100kpa compressor pressure ratio is 14 to 1 so p2/p1 = 14 but turbine efficiency is 85% and compressor efficienc
Consider the 2.0micrometer long GaAs device where the E-field is 5kV/cm and Mn*=.067M0. (a) Calculate the transit time of an electron through the device if the mobility is 8000 cm^2V-s. (b) The mean free path of an electron (average velocity x scattering time) is the average distance an electron travels between two consecu
Consider a bar of p-Si that is homogeneously doped to a value of 3x10^15 at T=300K. The applied electric field is zero. A light source is incident on the end of the semiconductor. The excess-carrier concentration generated at x=0 is deltap(0)=deltan(0)=10^13/cm^3. Neglect surface effects. Mun=1200/cm^2/Vs. Mup=400/cm^2/Vs.
Q. An n-type silicon sample with Nd=10^16cm-3 is steadily illuminated such that g'=10^21cm-s^-1. If tn0=tp0=10^-6s, calculate the position of the quasi-Fermi levels for electrons and holes with respect to the intrinsic level (assume that ni=1.5x10^10cm^-3).
Compare a nonuniform flow with the average velocity. See attachment for full problem including diagram.
The area of morecambe bar at high water is approx. 200km^2. At low water most of the bay is exposed sand. for this exercise, we could assume that on average the sand slopes evenly so that half way between high and low tide the area of water is 100km^2. The tidal range (between low and high tide) varies between 4m at neap tide
A player throws a ball with an initial velocity Vo of 15 m/s from a point A located 1.5 m above the floor. Knowing that the ceiling of the gymnasium is 6 m high, determine the highest point B at which the ball can strike the wall 18 m away. This problem was taken from the curvilinear motion of particles inside the kinematics
Womersly’s Problem: Plot some representative velocity profiles for the purely oscillatory flow of a Newtonian fluid in a long, rigid, straight pipe at various phases of the flow (3-4). For these plots, use the values of constants given below: Constants: Velocity (u): 105 cm/s Diamter (d): 2.23 cm Kinematic viscosit
Consider an ideal steam reheat and regenerative cycle where steam leaves a steam gen and enters a high pressure turbine at 3 Mpa and T=400 C and is extracted to an open feedwater heater at 0.8 Mpa. The remainder is reheated to 400 C at this pressure which flows to the low pressure turbine stage. The condenser saturation pressure
A gearbox operating under steady state conditions recieves 24 hp along the input shaft and delivers 10hp along the output shaft. The outer surface of the gearbox is at 110F and has an area of 1.4 ft^2. The temperature of the surroundings away from the immediate vicinity of the gearbox is 70 F. For the gear box, determine a) the
A diesel engine has air before compression at 280 K and 85 Kpa. The highest temperature is 2219 K and the highest pressure is 6 MPa. Find the volumetric compression ratio and the mean effective pressure using cold air properties at 300K.
How can be determined the dynamic parameters of a second order system, wiht an Inertia (M), a dampening coeficient ( C ) and a Stiffness constant ( K).
Elaborate a Matlab model for this, using an non reinforced second order equation. M*d2y/dt2 + C * dy/dt + K* y =0
Need to obtain a working mathematical model of the balance beam problem, preferably with a cart, not a ball. i.e. Newtons laws leading through to equations of motion, aswell as transfer functions for use in matlab, any help will be much appreciated, thank you...
A box beam made from an extruded aluminium ally having 5 414 mm wall thickness is loaded by an inclined force P=100 N, as shown in the figure. Determine the maximum stress on section a-b. For the box beam, use the centreline dimension for finding I. (Note that the stress is far away from the support where large local stress co
Simply supported (in 3 dimensions) wooden beam under constant load at an angle - find stresses and locate Neutral Axis
A 150  200 mm wooden beam shown in Fig 9-4 (a) is used to support a uniformly distributed load of 4 kN (total) on a simple span of 6000 mm. The applied load acts in a plane making an angle, , of 20 with the vertical, as shown in Fig 9-4 (b) and again in Fig. 9-4 (c). Calculate the maximum bending stress
(a) Design a hollow steel shaft to transmit 300 hp at 75 rpm without exceeding a shear tress of 8000 psi. Use 1.2:1 as the ratio of the outside diameter to the inside diameter. (b) What solid shaft could be used instead?