he desk has a weight of 80 lb and a centerof gravity at G. Determine the initial acceleration of a desk when the man applies enough force F to overcomethe static friction at A and B. Also, find the vertical reactions on each of the two legs at A and at B. Thecoefficients of static and kinetic friction at A andB are μs= 0.45 andμk= 0.25, respectively.

Answer:

[tex]N_a=\frac{45.04}{2}=22.52lb,N_b=\frac{67.48}{2} =33.74lb[/tex]

Explanation:

Na and Nb are the vertical reactions on each of the two legs at A and at B

For the horizontal forces:

[tex]Fcos(30)-0.5N_a-0.5N_b=0\\0.5N_a+0.5N_b= Fcos(30)\\N_a+N_b= 2Fcos(30)[/tex]

For the vertical forces:

[tex]N_a+N_b-Fsin(30)-75=0\\N_a+N_b=Fsin(30)+80[/tex]

Therefore equating both equations:

[tex]2Fcos(30)=Fsin(30)+80\\F(2cos(30)-sin(30))=80\\F=\frac{80}{2cos(30)-sin(30)} =64.93N[/tex]

After the desk star to slide:

sum of all vertical force = ma , therefore:

[tex]N_a+N_b-64.93sin(30)-80=0\\N_a+N_b=64.93sin(30)+80[/tex]

sum of all horizontal force = ma

[tex]64.93cos(30)-0.2N_a-0.2N_b=\frac{80lb}{32.2ft/s^2}a\\ 0.2(N_a+N_b)=64.93cos(30)-\frac{80lb}{32.2ft/s^2}a\\N_a+N_b=\frac{64.93cos(30)-\frac{80lb}{32.2ft/s^2}a}{0.2}=324.65-12.42a[/tex]

equating both equations:

[tex]324.65-12.42a=64.93sin(30)+80\\12.42a=324.65-64.93sin(30)-80\\12.42a=212.185\\a=17.08ft/s^2[/tex]

From the moment equation:

[tex]4N_b-80(2)-64.93(3)=\frac{-80}{32.2} (17.08)(2)\\N_b=67.48lb[/tex]

[tex]N_a=\frac{64.93cos(30)-\frac{80lb}{32.2ft/s^2}(17.08)}{0.2}-67.48 = 45.04lb[/tex]

For each leg: [tex]N_a=\frac{45.04}{2}=22.52lb,N_b=\frac{67.48}{2} =33.74lb[/tex]

The spherical pressure vessel has an inner diameter of 2 m and a thickness of 10 mm. A strain gauge having a length of 20 mm is attached to it, and it is observed to increase in length by 0.012 mm when the vessel is pressurized. Determine the pressure causing this deformation, and find the maximum in-plane shear stress, and the absolute maximum shear stress at a point on the outer surface of the vessel. The material is steel, for which Est

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Problem Statement: Air flows at a rate of 0.1 kg/s through a device as shown below. The pressure and temperature of the air at location 1 are 0.2 MPa and 800 K and at location 2 the pressure and temperature are 0.75 MPa and 700 K. The surroundings are at 300 K and the surface temperature of the device is 1000 K. Determine the rate that the device performs work on its surroundings if the rate of heat transfer from the surface of the device to the environment is 1 kW. Justify your answer. Note that the flow direction for the air is not specified so you need to consider all possibilities for the direction of the airflow. Assume that the air is an ideal gas, that R

Two Electric field vectors E1 and E2 are perpendicular to each other; obtain its base
vectors.

How does a car batteray NOT die?

The asymmetric roof truss is of the type used when a near normal angle of incidence of sunlight onto the south-facing surface ABC is desirable for solar energy purposes. The five vertical loads represent the effect of the weights of the truss and supported roofing materials. The 390-N load represents the effect of wind pressure. Determine the equivalent force-couple system at A. The couple is positive if counterclockwise, negative if clockwise. Also, compute the x-intercept of the line of action of the system resultant treated as a single force R.

Air at 100°F, 1 atm, and 10% relative humidity enters an evaporative cooler operating at steady state. The volumetric flow rate of the incoming air is 1765 ft3/min. Liquid water at 68°F enters the cooler and fully evaporates. Moist air exits the cooler at 70°F, 1 atm. There is no significant heat transfer between the device and its surroundings and kinetic and potential energy effects can be neglected. Determine the mass flow rate at which liquid enters, in lb(water)/min.

A thin‐walled tube with a diameter of 12 mm and length of 25 m is used to carry exhaust gas from a smoke stack to the laboratory in a nearby building for analysis. The gas enters the tube at 200°C and with a mass flow rate of 0.006 kg/s. Autumn winds at a temperature of 15°C blow directly across the tube at a velocity of 2.5 m/s. Assume the thermophysical properties of the exhaust gas are those of air

Estimate the average heat transfer coefficient for the exhaust gas flowing inside the tube.

A heat recovery device involves transferring energy from the hot flue gases passing through an annular region to pressurized water flowing through the inner tube of the annulus. The inner tube has inner and outer diameters of 24 and 30 mm and is connected by eight struts to an insulated outer tube of 60-mm diameter. Each strut is 3 mm thick and is integrally fabricated with the inner tube from carbon steel (k 50 W/m K). Consider conditions for which water at 300 K flows through the inner tube at 0.161 kg/s while flue gases at 800 K flow through the annulus, maintaining a convection coefficient of 100 W/m2 K on both the struts and the outer surface of the inner tube. What is the rate of heat transfer per unit length of tube from gas to the water?

Have you ever had an ice cream headache that’s when a painful sensation resonates in your head after eating something cold usually ice cream on a hot day this pain is produced by the dilation of a nerve center in the roof of your mouth the nerve center is overreacting to the cold by trying to hit your brain ice cream headaches have turned many smiles to frowns identify the structure

The supplement file* that enclosed to this homework consists Time Versus Force data. The first column in the file stands for time (second) and the 2nd stands for force (Volt), respectively. This data were retrieved during an impact event. In this test, an impactor strikes to a sample. A force-ring sensor that attached to the impactor generates voltage during collision. A data acquisition card gathers the generated signals.
• Take the mass of the impactor as 30 kg and strike velocity as 2.0 m/s.
• Pick the best numerical technique, justify your choice.
• All results must be in SI units.

a) Determine a factor that will be used in the conversion from V to N. The calibration data that supplied by manufacturer as below:
• Take the mass of the impactor as 30 kg and strike velocity as 2.0 m/s.
• Pick the best numerical technique, justify your choice.
• All results must be in SI units.

a) Determine a factor that will be used in the conversion from V to N. The calibration data that supplied by manufacturer as below:• Take the mass of the impactor as 30 kg and strike velocity as 2.0 m/s.
• Pick the best numerical technique, justify your choice.
• All results must be in SI units.

a) Determine a factor that will be used in the conversion from V to N. The calibration data that supplied by manufacturer as below:
b) Compute the impulse of this event.
c) Obtain acceleration, velocity and displacement histories by using Newton’s second law of motion.
d) Compute the absorbed energy during collision.

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b) Calculate the immediate (elastic) settlement.

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Assume that the waste strength is 170 mg/L BOD after primary clarification.

XA=MLSS = 2200 mg/L,
Xw = Xu = XR = 6,600 mg/L,
qc = 8 days.

Make sure you account for the solids in the discharge.

What volume of sludge (Qw=m3/day) is wasted each day from the secondary clarifiers?

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(USCS units) A deep drawing operation is performed on a sheet-metal blank that is 1/8 in thick. The height of the cup = 3.8 in and its diameter = 5.0 in (both inside dimensions).

(a) Assuming the punch radius = 0, compute the starting diameter of the blank to complete the operation with no material left in the flange.

(b) Is the operation feasible (ignoring the fact that the punch radius is too small)?

what is the Economic​

Consider this example of a recurrence relation. A police officer needs to patrol a gated community. He would like to enter the gate, cruise all the streets exactly once, and then leave by the same gate. What information would you need to determine a Euler circuit and a Hamilton circuit

A steady green traffic light means

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For an Ac signal with peak voltage Vp equal to 60V, the same power would be delivered to a load with a dc voltage of

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Your company has been retained to start steel erection for a project. The steel will be delivered on an 18-wheel flat-bed truck and then lifted into place. You will have a crane on site, a Grove GMK 5175 all-terrain crane and you will be lifting with ½ steel chains. The crane is a 175 Ton telescoping crane and the crane will be sitting on Type B soil. The steel delivery consists of 48 pieces of W18x65 structural steel, Grade A 36, broken down as follows and delivered in 12 bundles of 4 pieces each.

13 pieces - 25’ long
17 pieces -50’ long
18 pieces – 15’ long

Based on the above, answer the following questions:

a. Neglecting the weight of the truck, what is the total weight of the steel load?
b. Assuming that the steel will be bundled and lifted as follows, calculate the weight of each of the lifts

4 pieces of 15 feet long, W18x65 Weight_______________________
4 pieces of 50 feet long, W18x65 Weight_______________________
4 pieces of 25 feet long, W18x65 Weight_______________________

c. With the soil conditions noted above,

Will the crane be able to safely lift the heaviest lift?
i. Yes
ii. No

d. What will be the maximum amount or load that can be lifted by this crane using the boom length of 155 feet?

The supplement file* that enclosed to this homework consists Time Versus Force data. The first column in the file stands for time (second) and the 2nd stands for force (Volt), respectively. This data were retrieved during an impact event. In this test, an impactor strikes to a sample. A force-ring sensor that attached to the impactor generates voltage during collision. A data acquisition card gathers the generated signals.

Consider a Carnot heat pump cycle executed in a steady-flow system in the saturated mixture region using R-134a flowing at a rate of 0.264 kg/s. The maximum absolute temperature in the cycle is 1.15 times the minimum absolute temperature, and the net power input to the cycle is 5 kW. If the refrigerant changes from saturated vapor to saturated liquid during the heat rejection process, determine the ratio of the maximum to minimum pressures in the cycle.

Create an abstract class DiscountPolicy. It should have a single abstract method computeDiscount that will return the discount for the purchase of a given number of a single item. The method has two parameters, count and itemCost. 2. Derive a class BulkDiscount from DiscountPolicy, as described in the previous exercise. It should have a constructor that has two parameters, minimum and percent. It should define the method computeDiscount so that if the quantity purchased of an item is more than minimum, the discount is percent percent. 3. Derive a class BuyNItemsGetOneFree from DiscountPolicy, as described in Exercise 1. The class should have a constructor that has a single parameter n. In addition, the class should define the method computeDiscount so that every nth item is free. For example, the following table gives the discount for the purchase of various counts of an item that costs $10, when n is 3: count 1 2 3 4 5 6 7 Discount 0 0 10 10 10 20 20

4. Derive a class CombinedDiscount from DiscountPolicy, as described in Exercise 1. It should have a constructor that has two parameters of type DiscountPolicy. It should define the method computeDiscount to return the maximum value returned by computeDiscount for each of its two private discount policies. The two discount policies are described in Exercises 2 and 3. 5. Define DiscountPolicy as an interface instead of the abstract class described in Exercise 1.