midterm exam(mep521)

7/29/2019 Midterm Exam(MEP521)

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ROMBLON STATE UNIVERSITY

Odiongan, RomblonCOLLEGE OF ENGINEERING AND TECHNOLOGYDEPARTMENT OF MECHANICAL ENGINEERING

MIDTERM EXAM MEP 521Name: Date: Score:

MEP

Multiple Choice.Identify the correct answer that best completes the statement or answers the question. Write the letter only on the

space provided. No erasures allowed.

____ 1. This bolt class is commonly used in most automotive applications where there is increase in strength of the bolt.

a. Grade 2 b. Grade 5 c. Grade 8 d. Grade 12

____ 2. It is a device that consists of screw threads at both ends that is used for securing another member, as in bolting a steel

plate to concrete.

a. stove bolt b. stud bolt c. Turnbuckle d. U-bolt

____ 3. A metal pin having head on one end, inserted through aligned holes in the pieces to be joined then hammered on the

plain so as to form another head.

a. rivets b. screws c. Pins d. Bolt

____ 4. The ability of a material to withstand loads without breaking down is.

a. strain b. Strength c. stress d. endurance

____ 5. The ratio of ultimate stress to the factor of safety is.

a. Yield stress b. Ultimate stress c. Design stress d. elastic limit

____ 6. The maximum stress that would cause failure to the material after loads are being applied is.

a. Ultimate stress b. Yield stress c. True stress d. Design stress

____ 7. The maximum stress that will not cause failure even the force is repeatedly applied indefinitely.

a. Elastic limit b. Endurance limit c. Strength d. design stress

____ 8. A maximum shear stress occurs on the cross-section of the shaft at its_____ surface.a. innermost b. outermost c. middle d. Center

____ 9. The property of the material that permits permanent deformation before fracture in tension is.

a. Ductility b. Malleability c. Elasticity d. Brittleness

____ 10. The ability of a material to be deformed and to return to its original shape after the load are being applied.

a. Plasticity b. Elasticity c. Ductility d. Machinability

____ 11. A solid shaft transmits power at the rate of 2000 kW at the speed of 30 rpm. If the safe allowable stress is 80 MN/m ,

find the minimum diameter of the shaft.

a. 0.272 mm b. 0.372 mm c. 272.6 mm d. 343.5 mm

____ 12. Calculate the shaft diameter if the twist in the shaft is not to exceed 1 in 2m length. Shear strength is limited to 50

MN/m .(G = 100 GN/m ).

a. 80 mm b. 72 mm c. 83 mm d. 114 mm

____ 13. A torque of 1000 N-mm is applied to a 40 mm diameter rod of 3 m length. Determine the maximum shearing stress

induced in the rod. (G = 80 GN/m )

a.769 x 10 Pa

b.7.96 x 10 Pa

c.769 x 10 Pa

d.79.6 x 10 Pa


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MIDTERM EXAM MEP 521____ 14. A torque of 100,000 N-mm is applied to a 40 mm diameter rod of 5 m length. Determine the twist produced in the rod.

(G = 80 GN/m )

a. 1.46 b. 8.56 c. 5.56 d. 6.56

____ 15. For one propeller drive shaft, compute the outer surface shear stress when it is transmitting a torque of 1.76 KN-mm. The

shaft is hollow tube having an outside diameter of 60 mm and inside diameter of 40 mm.

a. 51.7 kPa b. 52 MPa c. 35 kPa d. 50 Pa

____ 16. For one propeller drive shaft, compute the inner surface shear stress when it is transmitting a torque of 1.76 KN-mm. The

shaft is hollow tube having an outside diameter of 60 mm and inside diameter of 40 mm.

a. 34. 5 kPa b. 34.5 Pa c. 34.5 mPa d. 38 kPa

____ 17. Shaft made up of two or more materials are called.

a. combined b. compound c. lineshaft d. complex

____ 18. The shaft are held fixed both ends. It carries a torque of 10,000 ft -lb, 15-in from one end to midpoint and 24-in from

midpoint to the other ends. Compute for the torque reactions.

a. 6,154/3,846 b. 46150/73600 c. 1,500/8,500 d. 4,160/5,840

____ 19. A hollow shaft must carry a torque of 3,400 N-mm at shearing stress of 55 mPa. The inside diameter is to be 0.65 of the

outside diameter. Find the outside diameter of the shaft.

a. 7.26 mm b. 52 mm c. 61 mm d. 72.63 mm

____ 20. For high strength requirements, a material for shafting is made of.

a. mild steel b. alloy steel c. low carbon d. stainless steel

____ 21. Maximum stress without causing deformation is called.

a. design stress b. ultimate stress c. yield stress d. shear stress

____ 22. Turbine shaft is is a form of.

a. machine shaft b. transmission shaft c. prime mover shaft d. lineshaft

____ 23. A short rotating shaft is often called as.

a. spindle b. axle c. Rotor d. mini-shaft

____ 24. A solid shaft of mild steel 200 mm in diameter is to be replaced by hollow shaft of allowable shear stress is 22% greater.

If the power to be transmitted is to be increased by 20% and the speed of rotation increased by 6%, determine the

maximum internal diameter of the hollow shaft. The external diameter of the hollow shaft is to be 200 mm.

a. 107.4 mm b. 106.4 mm c. 104.6 mm d. 103.9 mm

____ 25. A hollow shaft of external diameter 120 mm transmits 30 kW power at 200 rpm. Determine the maximum internal

diameter if the maximum stress in the shaft is not to exceed 60 N/mm .

a. 88.5 mm b. 92.1 mm c. 102 mm d. 67.5 mm

____ 26. What will happen to the stress of the shaft under torsion if its diameter will increase to one and a half.

a. it will increase 8 times c. it will increase half times

b. it will decrease 5 times d. no changes


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MIDTERM EXAM MEP 521____ 27. What will happen to the stress of the shaft under torsion, if its diameter will decrease one-half of its size.

a. it will decrease 5 times c. it will decrease 3 times

b. it will increase 8 times d. no changes

____ 28. What pitch must be provided on a square single thread power screw to raise a 1500 lb. weight at 38 fpm with power

consumption of 4 hp? The pitch diameter is 1.50-in., f = 0.15 and collar friction is negligible.

a. 1.55 b. 1.01 c. 1.78 d. 2.01

Short Answer: Write your answer on the blank space provided. Avoid erasures.

29. Find the moment of inertia for a solid shaft having 3-in. in diameter. ________

30. Find the moment of inertia for a rectangular beam with a 2.0-m x 10-in x 4-in dimension. ________

31. Given the data for the steel support on bridge:

Pull Force = 10 000 lbsFactor of safety = 5.0

Ultimate stress = 64 000 psi

Determine the size of the rod to be used. ________

Problem: Solve the problem correctly. Write only your final answer on the blank space provided. No erasures allowed.

32. A double threaded ACME screw is driven by a motor at 400 rpm. It is used to raise a nut attached with load of 9000 N at

12 m/min. The screw has 30 mm pitch diameter. Coefficient of friction of the threads is 0.15. Friction torque in the thrust

bearings of the motor is 20% of the total torque input. Determine the torque required to raise a load?

ANS._______

33. A double threaded ACME screw is driven by a motor at 400 rpm. It is used to raise a nut attached with load of 9000 N at

12 m/min. The screw has 30 mm pitch diameter. Coefficient of friction of the threads is 0.15. Friction torque in the thrustbearings of the motor is 20% of the total torque input. Determine the motor power required to raise the load?

ANS._______

34. A 55 mm solid shaft is to be replaced by a hollow shaft of equal strength and same material yet the hollow shaft weighs

only half as much of solid per unit length. Calculate the dimensions of hollow shaft required?

ANS.________

35. Find the factor of safety of a 25 mm x 50 mm steel plate if the load fluctuates from 450 kN to 270 kN. The ultimate

strength, yield strength and endurance strength of the plate are 900 Mpa, 700 Mpa and 300 Mpa respectively. Consider

the plate is ductile and stress factor of 1.81. ANS.________


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MIDTERM EXAM MEP 521ME Engineering Problems

Answer Section

MULTIPLE CHOICE

1. ANS: B PTS: 1

2. ANS: B PTS: 1

3. ANS: A PTS: 1

4. ANS: B PTS: 1

5. ANS: C PTS: 1

6. ANS: A PTS: 1

7. ANS: B PTS: 1

8. ANS: B PTS: 1

9. ANS: A PTS: 1

10. ANS: B PTS: 1

11. ANS: D PTS: 1

12. ANS: D

T = T = TL/JG

S = 16T/d

PTS: 1

13. ANS: D PTS: 1

14. ANS: A PTS: 1

15. ANS: A PTS: 1

16. ANS: A PTS: 1

17. ANS: B PTS: 1

18. ANS: B PTS: 1

19. ANS: A PTS: 1

20. ANS: B PTS: 1


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MIDTERM EXAM MEP 52121. ANS: C PTS: 1

22. ANS: C PTS: 1

23. ANS: A PTS: 1

24. ANS: D

PH = 1.20 Ps

(2p.NH.TH)/60 = (2p.Ns.Ts)/60 1.20

NH.TH = 1.20 Ns.Ts

PTS: 1

25. ANS: A PTS: 1

26. ANS: B PTS: 1

27. ANS: B PTS: 1

28. ANS: A PTS: 1

SHORT ANSWER

29. ANS: 3.97 in4

I = D

PTS: 1

30. ANS: 53.33 in4

I = bh /12

PTS: 1

31. ANS:

St = F/A = Su/N

D = 0.71 in

PTS: 1

PROBLEM

32. ANS:

T = 60.18 N-m

PTS: 1

33. ANS:

2.52 kW = 3.5 hp


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MIDTERM EXAM MEP 521PTS: 1

34. ANS:

do = 66.4 mm

di = 53.8 mm

PTS: 1

35. ANS:

= 1.18

1/N = Sm/Sy + kt(Sa/Sn)

PTS: 1

midterm exam(mep521)

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