1. In order to test the efficiency of reducer gear train 1 kW input was given at the input end at a speed of 1440 rpm and at the output end the measured torque was 56.36 Nm. If the ratio of speed reduction in this unit is 10: 1, the efficiency is about

1. 1. 78%

   
   
   

   2. 85%

   
   
   

   3. 63%

   
   
   

   4. 96%

   
   
   

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1. View Hint View Answer Discuss in Forum

   Speed reduction = 10: 1
   

   Output speed =	1440	= 144 rpm
   	10

   
   

   Output Torque = T.ω = 56.36 ×	2π × 144	= 849.88 N - m
   	60

   
   

   % efficiency =	Output	× 100
   	Input

   
   

   =	849.88	× 100 = 85 %(Approximately)
   	1000

   Correct Option: B

   Speed reduction = 10: 1
   

   Output speed =	1440	= 144 rpm
   	10

   
   

   Output Torque = T.ω = 56.36 ×	2π × 144	= 849.88 N - m
   	60

   
   

   % efficiency =	Output	× 100
   	Input

   
   

   =	849.88	× 100 = 85 %(Approximately)
   	1000

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2. Which of the bearings given below SHOULD NOT be subjected to a thrust load?

1. 1. Deep groove ball bearing

   
   
   

   2. Angular contact ball bearing

   
   
   

   3. Cylindrical (straight) roller bearing

   
   
   

   4. Single row tapered roller bearing

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   NA

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3. A horizontal plate has been joined to a vertical to a vertical post using four rivets arranged as shown in the figure. The magnitude of the load on the worst loaded rivet (in N) is _______.
   

1. 1. 1758.83 N

   
   
   

   2. 1625.83 N

   
   
   

   3. 1839.83 N

   
   
   

   4. 1436.89 N

   
   
   

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1. View Hint View Answer Discuss in Forum

   Primary force (P₁) = 100 N
   

   P"1 = P"2 = P"3 = P"4 =	Pe × r
   	4r²

   
   

   =	400 × 500 ×		40√2
   			2
   	4 ×		40√2
   			2

   
   = P"₁ = 1767.766N
   1 & 4 are worst loaded
   ∴ (P_net)² = (P₁)² + (P"₂)² + 2(P₁)(P"₁) cos 45°
   P_net = 1839.83 N

   Correct Option: C

   Primary force (P₁) = 100 N
   

   P"1 = P"2 = P"3 = P"4 =	Pe × r
   	4r²

   
   

   =	400 × 500 ×		40√2
   			2
   	4 ×		40√2
   			2

   
   = P"₁ = 1767.766N
   1 & 4 are worst loaded
   ∴ (P_net)² = (P₁)² + (P"₂)² + 2(P₁)(P"₁) cos 45°
   P_net = 1839.83 N

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4. If the rivets are to be designed to avoid crushing failure, the maximum permissible load P in kN is

1. 1. 7.50

   
   
   

   2. 15.00

   
   
   

   3. 22.50

   
   
   

   4. 30.00

   
   
   

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1. View Hint View Answer Discuss in Forum

   For rivet,
   

   σ	P	=	P
   	3Ar		3d × t

   
   ∴ P_s = 100 × d × t × 3 = 15 kN
   and P_c = 150 × d × t × 3 = 22.5 kN
   ∴ p = max (15, 22.5) = 22.5 kN

   Correct Option: C

   For rivet,
   

   σ	P	=	P
   	3Ar		3d × t

   
   ∴ P_s = 100 × d × t × 3 = 15 kN
   and P_c = 150 × d × t × 3 = 22.5 kN
   ∴ p = max (15, 22.5) = 22.5 kN

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5. A cylindrical shaft is subjected to an alternating stress of 100 MPa. Fatigue strength to sustain 1000 cycles is 490 MPa. If the corrected endurance strength is 70 MPa, estimated shaft life will be

1. 1. 1071 cycles

   
   
   

   2. 15000 cycles

   
   
   

   3. 281914 cycles

   
   
   

   4. 928643 cycles

   
   
   

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1. View Hint View Answer Discuss in Forum

   
   By concept of straight line,
   

   y - 1.8451	=	1.8451 - 2.6902
   x - 6		6 - 3

   
   At y = 2
   ⇒ x = 5.4501
   log10_N = 5.4501, N = 281914

   Correct Option: C

   
   By concept of straight line,
   

   y - 1.8451	=	1.8451 - 2.6902
   x - 6		6 - 3

   
   At y = 2
   ⇒ x = 5.4501
   log10_N = 5.4501, N = 281914

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