21. A band brake having bandwidth of 80 mm, drum diameter of 250 mm, coefficient of friction of 0.25 and angle of wrap of 270 degrees is required to exert a friction torque of 1000 N m. The maximum tension (in kN) developed in the band is

1. 1. 1.88

   
   
   

   2. 3.56

   
   
   

   3. 6.12

   
   
   

   4. 11.56

   
   
   

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1. View Hint View Answer Discuss in Forum

   Given: b = 80 mm = 0.08 m D = 250 mm = 0.25
   

   R =	D	= 0.25
   	2

   
   μ = 0.25
   

   θ = 270° = 270 ×	π	= 4.712 radians
   	180

   
   F_t = 100 N-m
   

   As	p1	= eμθ
   	p2

   
   ⇒  p₁ = e^μθ ⋅ p₂ = e^{0.25 × 4.712} ⋅ p₂ = 3.25p₂
   Now, F_t = (p₁ − p₂)R
   

   ∴  1000 =		p1 −	p1		0.125
   			3.25

   
   Solving, we get maximum tension in the belt,
   p₁ = 11.56 kN

   Correct Option: D

   Given: b = 80 mm = 0.08 m D = 250 mm = 0.25
   

   R =	D	= 0.25
   	2

   
   μ = 0.25
   

   θ = 270° = 270 ×	π	= 4.712 radians
   	180

   
   F_t = 100 N-m
   

   As	p1	= eμθ
   	p2

   
   ⇒  p₁ = e^μθ ⋅ p₂ = e^{0.25 × 4.712} ⋅ p₂ = 3.25p₂
   Now, F_t = (p₁ − p₂)R
   

   ∴  1000 =		p1 −	p1		0.125
   			3.25

   
   Solving, we get maximum tension in the belt,
   p₁ = 11.56 kN

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22. For full depth of involute spur gears, minimum number of teeth of pinion to avoid interference depends upon

1. 1. pressure angle

   
   
   

   2. speed ratio

   
   
   

   3. circular pitch

   
   
   

   4. pitch diameter

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: A

   NA

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23. For full depth of involute spur gears, minimum number of teeth of pinion to avoid interference depends upon

1. 1. pressure angle

   
   
   

   2. speed ratio

   
   
   

   3. circular pitch

   
   
   

   4. pitch diameter

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: A

   NA

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24. Modern gear tooth profile is given involute shape because

1. 1. this is a very easy curve for manufacturing

   
   
   

   2. sliding does not takes place anywhere on meshing teeth

   
   
   

   3. involute is the only profile that gives conjugate action

   
   
   

   4. change in the centre distance does not change gear ratio

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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25. The basic load rating of a ball bearing is

1. 1. the maximum static radial load that can be applied without causing any plastic deformation of bearing components

   
   
   

   2. the radial load at which 90% of the group of apparently identical bearings run for on million revolutions before the first evidence of failure

   
   
   

   3. the maximum radial load that can be applied during operation without any plastic deformation of bearing components

   
   
   

   4. a combination of radial and axial loads that can be applied without any plastic deformation

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: B

   NA

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