586. The optimum pouring time for a casting depends on several factors. One important factor among them is

1. 1. location of riser

   
   
   

   2. porosity of sand mould

   
   
   

   3. fluidity of casting metal

   
   
   

   4. area of the pouring basin

   
   
   

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1. View Hint View Answer Discuss in Forum

   Higher the fluidity, flow will be easier

   Correct Option: B

   Higher the fluidity, flow will be easier

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587. Assertion (A): Converging passage is used for feeding liquid metal into a mould.
     Reason (R): Inhalation of air promotes blow holes in casting.

1. 1. Both (A) and (R) are true and (R) is the correct reason for (A)

   
   
   

   2. Both (A) and (R) are true but (R) is NOT the correct reason for (A)

   
   
   

   3. Both (A) and (R) are false

   
   
   

   4. (A) is false but (R) is true

   
   
   

   5. None of these

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: E

   NA

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588. What is the velocity of the steel at the bottom of the sprue if the sprue height is 30 cm? Assume the frictional and other losses to be 20%.

1. 1. 4.17 m/s

   
   
   

   2. 1.17 m/s

   
   
   

   3. 2.17 m/s

   
   
   

   4. 3.17 m/s

   
   
   

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1. View Hint View Answer Discuss in Forum

   V = √2gh × 0.8
   = √2 × 9.81 × 0.3 × 0.8
   = 2.17 m/s

   Correct Option: C

   V = √2gh × 0.8
   = √2 × 9.81 × 0.3 × 0.8
   = 2.17 m/s

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589. The figure shows a pouring arrangement for casting of a metal block. Frictional losses are negligible. The acceleration due to gravity is 9.81 m/s². The time (in s, round off to two decimal places) to fill up the mold cavity (of size 40 cm × 30 cm × 15 cm) is ____.
     

1. 1. 28.921s

   
   
   

   2. 28.92s

   
   
   

   3. 28.93s

   
   
   

   4. 28.90s

   
   
   

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1. View Hint View Answer Discuss in Forum

   Mold filling time, tm =	Vm
   	Ag ⋅ √2gh

   
   

   =	40 × 30 × 15
   	π(2)²	× √2 × 9.81 × 100 ×20
   	4

   
   t = 28.923 sec. ≈ 28.92s

   Correct Option: B

   Mold filling time, tm =	Vm
   	Ag ⋅ √2gh

   
   

   =	40 × 30 × 15
   	π(2)²	× √2 × 9.81 × 100 ×20
   	4

   
   t = 28.923 sec. ≈ 28.92s

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590. In a casting process, a vertical channel through which molten metal flows downward from pouring basin to runner for reaching the mould cavity is called

1. 1. riser

   
   
   

   2. blister

   
   
   

   3. pin hole

   
   
   

   4. sprue

   
   
   

   5. None of these

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: E

   NA

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