Mechanical Engineering Answers

Find the acceleration of the 

three weights shown in fig. Assume 

pulleys are frictionless. Also find 

the tension in the cables.

Two stations A and B are 10 km apart in a straight track, and a train starts from A and 

comes to rest at B. For three quarters of the distance, the train is uniformly accelerated and 

for the remainder distance uniformly retarded. If it takes 15 minutes over the whole 

journey, find its acceleration, retardation and the maximum speed it attains.

A flywheel rotates with a constant retardation due to breaking from t=0to t=10 seconds. it made 400 revolutions . At time t=8 sec , it's angular velocity was 45πrad/sec. Determine

1 . Value of constant ratardation.

2. Total time taken to come to rest.

3. Total revolution made till it comes to rest.

i. A fixed mass of gas has a pressure of 1.2 MPa and volume of 0.3 m3 and temperature of 100 oC . The pressure is changed to 400 kPa and the volume changed to 0.06 m3. Determine the new temperature?

ii. A mass of gas is stored in a cylinder. The gas is stored at a pressure of 1.2 MPa and the cylinder has a volume of 0.03 m3 and temperature of 100 oC , Find the mass of the gas. The characteristic gas constant for air is 300 Jkg−1K−1.

Calculate the efficiency of an ice making machine that takes in water at 10°C and produces ice at a temperature of -7°C. Water is taken in at a rate of 1 kg every 4 minutes. The input power of the machine is 400 W. 

The specific heat capacity of water is 4187 Jkg−1K−1 and its specific latent heat of fusion is 334 Jkg−1.

A brass tie bar of length 500 mm and diameter 20 mm undergoes a change in temperature from 25°C to 135°C. The linear expansivity of copper is 19 × 10−6°C−1 and its modulus of elasticity is 84 Gpa.

i)​Determine the change of length that takes place.

ii)​Determine the compressive force induced in the bar if it is rigidly held and expansion is prevented.

A balanced-flow ERV is used to ventilate a warehouse at a rate of 1,000 L/s. The air conditions within the warehousearequitecoolanddry,Tdb=10°CandRH=50%.Ataparticularmoment,theoutsideairenters theERVatTdb=38°CandRH=40%.Duringthistime,theairconditionsleavingtheERVontheexhaustside are measured to be Tdb= 31°Cand RH =35%.a)Estimate the Sensible-Effectiveness (%) of theERV.b)Estimate the Latent-Effectiveness (%) of theERV.c)Estimate the drybulb temperature (°C) and relative humidity (%) leaving the ERV on the fresh-airside.d)Plot the conditions of all four air-streams (i.e.,fresh-air, entering and leaving; exhaust-air, entering and leaving) on a psychrometricchart.

A balanced-flow ERV is used to ventilate a warehouse at a rate of 1,000 L/s. The air conditions within the warehousearequitecoolanddry,Tdb=10°CandRH=50%.Ataparticularmoment,theoutsideairenters theERVatTdb=38°CandRH=40%.Duringthistime,theairconditionsleavingtheERVontheexhaustside are measured to be Tdb= 31°Cand RH =35%.a)Estimate the Sensible-Effectiveness (%) of theERV.b)Estimate the Latent-Effectiveness (%) of theERV.c)Estimate the drybulb temperature (°C) and relative humidity (%) leaving the ERV on the fresh-airside.d)Plot the conditions of all four air-streams (i.e.,fresh-air, entering and leaving; exhaust-air, entering and leaving) on a psychrometricchart.

In the process to determine the position of the A TALL BUILDING at inaccessible location, explain in detail the steps to determine the location and the coordinates of the top of the BUILDING. Beside the coordinates, the height of the BUILDING and the reduced level at the top of the BUILDING needs to be determined. All the bearings, distances and coordinates of the control stations nearby the location of the tower are known value as shown in figure below. Nearby Bench Mark (BM) with a known reduced level can be utilized in this survey which is 22. The distance from the tower to the nearest control station is about 350 - 400 m. 

Bearing and distance for the control stations;

From To Bearing Distance

A

B 246°30’20” 115.333 m

C 292°45’10” 149.675 m

D 312°20’30” 162.931 m

E 333°04’40” 120.553 m

F 274°55’00” 178.025 m

G 251°40’10” 196.987 m

H 275°30’50” 225.818 m

SHOW the calculation

A cube of edge 24mm is resting on the top of a frustum of cone of base diameter 60mm and top 

diameter of 40mm with axis height of 72mm. Draw the isometric view of these solids