Mechanical Engineering Answers

The speed of a vehicle is reduced with a constant acceleration from 72km/h

72km/h to 18 km/h

km/h over 250m

250m directly down an incline of 1in25

1in25. The mass of the vehicle is 1.9 Mg

Mg and it has a constant resistance to motion of 350N

350N. 

Calculate the magnitude of the braking Force

a steam engine working on Rankine cycle operates between 1.96Mpa, 250degree celsius and 13.7Kpa. If engine consumes steam at the rate of 0.086kg per second, determine rankine cycle efficiency, neglecting pump work. Also, find Rankine cycle effeciency considering pump work.

A company purchased an equipment with the initial cost of 50000$. The annual operating cost of the equipment is 9000$ per year. There is a major maintenance cost of 20000$ at 6th year. The salvage value of the equipment is 6000$. Find the net present value if the useful life of the equipment is 9 years, considering interest rate is 10%/year. 

1- In the casting of steel under certain mold conditions, the mold constant in Chvorinov's Rule is 

known to be 4.0 min/cm2

, based on previous experience. The casting is a plate (fig. 1) whose 

length l = 30 cm, width w = 10 cm, and thickness/height h = 20 mm. Determine the time it will 

take for the casting to solidify.

1. Determine the number of atoms in 1.75 mol Al

2. Calculate the number of formula units in 25.0 mol NaNO3

3. Given 6.25 mol H O2 determine the number of molecules.

DIRECTIONS: A. How many atoms are in each of the following samples? .

11.3 .44.2 a g Pb

b g Mg

B. Calculate the mass in grams of each of the following samples. 18 21 4 .

1.50x10 .8.35x10 a atoms Ne

b molecules CH 1. What is the percent composition of the following compounds?

0 8 12 22 11 2 4 3 . ( ) . ( ) . min ( ( )

a Naphtalene C H

b Sucrose C H O

c.Alu um sulfate Al SO

The crank and connecting rod of a reciprocating engine are 150 mm and 600 mm respectively. The crank makes an angle of 60° with the inner dead center and revolves at a uniform speed of 300 r.p.m. Find, by Klein’s construction,

1. Velocity and acceleration of the piston,

2. Velocity and acceleration of the mid-point D of the connecting rod, and

3. Angular velocity and angular acceleration of the connecting rod.

a 2,4 high container in a chemical plant stores three separate chemicals ,one on top of each other .These chemicals have densities of 1450 kg/m^3,550kg/m^3 respectively. Each chemical has a height of 0,8 m. Determine the total force on the 1,5 m side of the container and where it acts

the face of a dam is vertical to a depth of 5 m below the water surface and then slopes at 30 degrees to the vertical. If the depth of the water is 9 m,completely specify the resultant force per metre run acting on the whole face. Use equilibrium of vector to find the final answer

A gas turbine operating on a simple Joule cycle has a pressure compression ratio of 8:1. The turbine has a thermal efficiency of 60% of the ideal. Determine the actual thermal efficiency.

A Butchery at Western Cape requires a modularized trolley designed for 300 Kg maximum

load bearing capacity.

The information obtained is as follows:

I. The trolley will be shipped to the location using a drone that can lift 20 Kg maximum load

II. The drone has a standard box compartment measuring 1000 mm length, 600 mm width, and

300 mm depth.

(Assume the square meter weight of most 

solid flat sheets suitable for the trolley design is 3 Kg/m2

. Furthermore, assume the following

weights for materials that are available off the shelf: 

 Bearings: 200 g/bearing

 Rubberized wheel: 100 g/wheel

 Helical springs: 50 g/spring

 Cylindrical shaft: 20 g/mm diametral volume for 1000 mm length

 Standard trolley handle: 40 g