What is the critical rotation speed in revolutions per second, for a ball mill of 1.2 m diameter charged with 70 mm dia balls? (A) 0.5 (B) 1.0 (C) 2.76 (D) 0.66

What is the critical rotation speed in revolutions per second, for a ball
mill of 1.2 m diameter charged with 70 mm dia balls?
(A) 0.5
(B) 1.0
(C) 2.76
(D) 0.66
by

1 Answer

Answer :

(D) 0.66
by

Related questions

In a ball mill, the volume occupied by the balls (when the mill is stopped) is about __________ percent of the volume of the mill. (A) 35 (B) 50 (C) 70 (D) 85

Description : In a ball mill, the volume occupied by the balls (when the mill is stopped) is about __________ percent of the volume of the mill. (A) 35 (B) 50 (C) 70 (D) 85

Last Answer : (B) 50

A tube mill as compared to a ball mill (A) Employs smaller balls (B) Gives finer size reduction but consumes more power (C) Has larger length/diameter ratio (>2 as compared to 1 for ball mill) (D) All (A), (B) and (C)

Description : A tube mill as compared to a ball mill (A) Employs smaller balls (B) Gives finer size reduction but consumes more power (C) Has larger length/diameter ratio (>2 as compared to 1 for ball mill) (D) All (A), (B) and (C)

Last Answer : (D) All (A), (B) and (C)

Tube mill compared to ball mill (A) Produces finer products (B) Is long in comparison with its diameter (C) Uses smaller balls (D) All (A), (B) & (C)

Description : Tube mill compared to ball mill (A) Produces finer products (B) Is long in comparison with its diameter (C) Uses smaller balls (D) All (A), (B) & (C)

Last Answer : (D) All (A), (B) & (C)

A tube mill compared to a ball mill (A) Has a higher length/diameter ratio(B) Produces a coarser product(C) Has a higher diameter/length ratio(D) Uses much larger balls

Description : A tube mill compared to a ball mill (A) Has a higher length/diameter ratio (B) Produces a coarser product (C) Has a higher diameter/length ratio (D) Uses much larger balls

Last Answer : (A) Has a higher length/diameter ratio

Critical speed of rotation, N (in rps - rotation per second) of a trammel is equal to (where, g = acceleration due to gravity = 9.81 m/sec 2 and, r = radius of trammel, metre.) (A) (1/2π). √(g/r) (B) (1/π). √(g/r) (C) ½ √(g/r) (D) 2π. √(g/r)

Description : Critical speed of rotation, N (in rps - rotation per second) of a trammel is equal to (where, g = acceleration due to gravity = 9.81 m/sec 2 and, r = radius of trammel, metre.) (A) (1/2π). √(g/r) (B) (1/π). √(g/r) (C) ½ √(g/r) (D) 2π. √(g/r)

Last Answer : (A) (1/2π). √(g/r)

Theoretical capacity of crushing rolls in tons/hr is given by (where, V = peripheral velocity, m/sec. W = width of rolls, m Dr = distance between rolls ρ = density of material to be crushed, kg/m3 here, V =πND where, N = speed of the rolls in rotation per second (rps) D = diameter of rolls, m). (A) 3.6 V.W.Dr.ρ (B) 3.6 V.W. ρ (C) 3.6 W.Dr.ρ (D) 3.6 V.W.Dr/ρ

Description : Theoretical capacity of crushing rolls in tons/hr is given by (where, V = peripheral velocity, m/sec. W = width of rolls, m Dr = distance between rolls ρ = density of material to be crushed, kg/m3 here, V =πND where, N = speed of the rolls ... V.W.Dr.ρ (B) 3.6 V.W. ρ (C) 3.6 W.Dr.ρ (D) 3.6 V.W.Dr/ρ

Last Answer : (A) 3.6 V.W.Dr.ρ

Pulverised coal passing through 200 mesh screen has a diameter of 0.074 mm (74 micron). The same passing through 50 mesh screen will have a dia of __________ mm. (A) 0.007 (B) 0.30 (C) 50 (D) 0.014

Description : Pulverised coal passing through 200 mesh screen has a diameter of 0.074 mm (74 micron). The same passing through 50 mesh screen will have a dia of __________ mm. (A) 0.007 (B) 0.30 (C) 50 (D) 0.014

Last Answer : (B) 0.30

rpm of a trommel at critical speed is given by (where, D = Diameter of trommel in ft) (A) 76.65/D (B) 76.65/√D (C) 76.65/D2 (D) 76.75 √D

Description : rpm of a trommel at critical speed is given by (where, D = Diameter of trommel in ft) (A) 76.65/D (B) 76.65/√D (C) 76.65/D2 (D) 76.75 √D

Last Answer : (B) 76.65/√D

The operating speed of a ball mill should be __________ the critical speed. (A) Less than (B) Much more than (C) At least equal to (D) Slightly more than

Description : The operating speed of a ball mill should be __________ the critical speed. (A) Less than (B) Much more than (C) At least equal to (D) Slightly more than

Last Answer : (A) Less than

Actual operating speed of a ball mill may vary from 65 to 80% of the critical speed. Which of the following duties would require the ball mill to be operated at maximum percentage of critical speed? (A) Wet grinding in low viscous suspension (B) Wet grinding in high viscous suspension (C) Dry grinding of large particles (upto 1.25 cms) (D) Dry grinding of large particles in un-baffed mills

Description : Actual operating speed of a ball mill may vary from 65 to 80% of the critical speed. Which of the following duties would require the ball mill to be operated at maximum percentage of critical speed? (A) ... of large particles (upto 1.25 cms) (D) Dry grinding of large particles in un-baffed mills

Last Answer : (D) Dry grinding of large particles in un-baffed mills

Critical Speed (Nc ) of a ball mill is given by (where R1 and R2 are radii of ball mill and the ball respectively). (A) Nc = (1/4π). √(g/R1 - R2 ) (B) Nc = (1/2π). √(g/R1 - R2 ) (C) Nc = (1/π). √(g/R1 - R2 ) (D) Nc = (1/2π). √(R1 - R2 /g)

Description : Critical Speed (Nc ) of a ball mill is given by (where R1 and R2 are radii of ball mill and the ball respectively). (A) Nc = (1/4π). √(g/R1 - R2 ) (B) Nc = (1/2π). √(g/R1 - R2 ) (C) Nc = (1/π). √(g/R1 - R2 ) (D) Nc = (1/2π). √(R1 - R2 /g)

Last Answer : (B) Nc = (1/2π). √(g/R1 - R2 )

In case of a ball mill, (A) Coarse feed requires a larger ball (B) Fine feed requires a larger ball (C) Operating speed should be more than the critical speed (D) None of these

Description : In case of a ball mill, (A) Coarse feed requires a larger ball (B) Fine feed requires a larger ball (C) Operating speed should be more than the critical speed (D) None of these

Last Answer : (A) Coarse feed requires a larger ball

For efficient grinding, ball mills must be operated (A) At a speed less than the critical speed (B) At a speed more than the critical speed (C) At a speed equal to the critical speed (D) With minimum possible small balls

Description : For efficient grinding, ball mills must be operated (A) At a speed less than the critical speed (B) At a speed more than the critical speed (C) At a speed equal to the critical speed (D) With minimum possible small balls

Last Answer : (A) At a speed less than the critical speed

. A 0.5 m high bed made up of a 1 mm dia glass sphere (density 2500 kg/m3 ) is to be fluidised by water (density 1000 kg/m3 ). If at the point of incipient fluidisation, the bed voidage is 40%, the pressure drop across the bed is (A) 4.4 KPa (B) 2.94 KPa (C) 3.7 KPa (D) None of these

Description : . A 0.5 m high bed made up of a 1 mm dia glass sphere (density 2500 kg/m3 ) is to be fluidised by water (density 1000 kg/m3 ). If at the point of incipient fluidisation, the bed voidage is 40%, the pressure drop across the bed is (A) 4.4 KPa (B) 2.94 KPa (C) 3.7 KPa (D) None of these

Last Answer : (A) 4.4 KPa

The main differentiation factor between tube mill and ball mill is the (A) Length to diameter ratio (B) Size of the grinding media (C) Final product size (D) Operating speed

Description : The main differentiation factor between tube mill and ball mill is the (A) Length to diameter ratio (B) Size of the grinding media (C) Final product size (D) Operating speed

Last Answer : (A) Length to diameter ratio

__________ balls capable of grinding the feed in a ball mill gives the maximum efficiency. (A) Cast iron (B) Minimum size (C) Maximum size (D) Elliptical

Description : __________ balls capable of grinding the feed in a ball mill gives the maximum efficiency. (A) Cast iron (B) Minimum size (C) Maximum size (D) Elliptical

Last Answer : (B) Minimum size

A __________ mixer resembles a ball mill without balls. (A) Banbury (B) Pug mill (C) Tumbling (D) Pan

Description : A __________ mixer resembles a ball mill without balls. (A) Banbury (B) Pug mill (C) Tumbling (D) Pan

Last Answer : (C) Tumbling

Balls in a ball mill are usually made of (A) Steel (B) Cast iron (C) Stainless steel (D) Bronze

Description : Balls in a ball mill are usually made of (A) Steel (B) Cast iron (C) Stainless steel (D) Bronze

Last Answer : (A) Steel

The diameter of hole for 20 dia rivet shall be a) 23 mm b) 18 mm c) 21.5 mm* d) 22 mm

Description : The diameter of hole for 20 dia rivet shall be a) 23 mm b) 18 mm c) 21.5 mm* d) 22 mm

Last Answer : c) 21.5 mm*

The critical speed of a trommel (N) is related to its dia (D) as (A) N ∝ 1/√D (B) N ∝ √D (C) N ∝ D (D) N ∝ 1/D

Description : The critical speed of a trommel (N) is related to its dia (D) as (A) N ∝ 1/√D (B) N ∝ √D (C) N ∝ D (D) N ∝ 1/D

Last Answer : (A) N ∝ 1/√D

In ball mill operation, the feed size (Df in meters) and the ball diameter (Db in metres) are related as (where, K = grindability constant (varying from 0.9 to 1.4 in increasing order of hardness)) (A) Db 2 = K.Df (B) Db = K.Df (C) Db 3 = K.Df (D) Db 2 = K.Df

Description : In ball mill operation, the feed size (Df in meters) and the ball diameter (Db in metres) are related as (where, K = grindability constant (varying from 0.9 to 1.4 in increasing order of hardness)) (A) Db 2 = K.Df (B) Db = K.Df (C) Db 3 = K.Df (D) Db 2 = K.Df

Last Answer : (A) Db 2 = K.Df

The settling velocity of a spherical particle of diameter less than 0.1 mm as per Stock’s law, is A. Vs = 418 (Gs – Gw) d [(3T + 70)/100] B. Vs = 418 (Gs – Gw)d² [(3T + 70)/100] C. Vs = 218 (Gs – Gw)d² [(3T + 70)/100] D. Vs = 218 (Gs – Gw)d [(3T + 70)/100]

Description : The settling velocity of a spherical particle of diameter less than 0.1 mm as per Stock’s law, is A. Vs = 418 (Gs – Gw) d [(3T + 70)/100] B. Vs = 418 (Gs – Gw)d² [(3T + 70)/100] C. Vs = 218 (Gs – Gw)d² [(3T + 70)/100] D. Vs = 218 (Gs – Gw)d [(3T + 70)/100]

Last Answer : ANS: B

A hollow shaft of 1 m length is designed to transmit a power of 30 kW at 700 rpm. The maximum permissible angle of twist in the shaft is 1o. The inner diameter of the shaft is 0.7 times the outer diameter. The modulus of rigidity is 80 GPa. The outside diameter (in mm) of the shaft is _______. (a) 43 to 45 (b) 50to 60 (c) 70 to 80 (d) 85 to 100

Description : A hollow shaft of 1 m length is designed to transmit a power of 30 kW at 700 rpm. The maximum permissible angle of twist in the shaft is 1o. The inner diameter of the shaft is 0.7 times the outer diameter. The modulus of ... shaft is _______. (a) 43 to 45 (b) 50to 60 (c) 70 to 80 (d) 85 to 100

Last Answer : (a) 43 to 45

Power required for mixing Newtonian fluids is a function of the (A) Speed of impeller, diameter of impeller & viscosity (B) Density & viscosity of fluid only (C) Density of fluid, viscosity of fluid & impeller dia only (D) None of these

Description : Power required for mixing Newtonian fluids is a function of the (A) Speed of impeller, diameter of impeller & viscosity (B) Density & viscosity of fluid only (C) Density of fluid, viscosity of fluid & impeller dia only (D) None of these

Last Answer : (D) None of these

How to calculate the rate of rotation, in revolutions per minute.

Description : How to calculate the rate of rotation, in revolutions per minute.

Last Answer : answer:I’m going with 1.56 revs/min. Circumference = pi*d = 376.8 m Rate of rotation = 9.8 m/s, so it takes 38.4s to complete one rev. 60/38.4 = 1.56

In finish machining of an island on a casting with CNC milling machine, an end mill with 10 mm diameter is employed. The corner points of the island are represented by (0, 0), (0, 30), (50, 30) and (50, 0). By applying cutter radius right compensation, the trajectory of the cutter will be a.(-5, 0), (-5, 35), (55, 35), (55,-5), (-5,-5) b.(0,-5), (55,-5), (55, 35), (-5, 35), (-5,-5) c.(5, 5), (5, 25), (45, 25), (45, 5), (5, 5) d.(5, 5), (45, 5), (45, 25), (5, 25), (5, 5)

Description : In finish machining of an island on a casting with CNC milling machine, an end mill with 10 mm diameter is employed. The corner points of the island are represented by (0, 0), (0, 30), (50, 30) and (50, 0). By applying cutter radius right ... , 5), (5, 5) d.(5, 5), (45, 5), (45, 25), (5, 25), (5, 5)

Last Answer : a.(-5, 0), (-5, 35), (55, 35), (55,-5), (-5,-5)

Power required to drive a ball mill with a particular ball load is proportional to (where, D = diameter of ball mill.) (A) D (B) 1/D (C) D2.5 (D) 1/D2.5

Description : Power required to drive a ball mill with a particular ball load is proportional to (where, D = diameter of ball mill.) (A) D (B) 1/D (C) D2.5 (D) 1/D2.5

Last Answer : (C) D2.5 (D) 1/D2

Length/diameter ratio of a ball mill is (A) 1.5 (B) 1 (C) < 1 (D) > 1

Description : Length/diameter ratio of a ball mill is (A) 1.5 (B) 1 (C) < 1 (D) > 1

Last Answer : (C) < 1

The capillary rise of mercury is maximum in glass tube of dia __________ mm. (A) 0.5 (B) 1 (C) 2 (D) 5

Description : The capillary rise of mercury is maximum in glass tube of dia __________ mm. (A) 0.5 (B) 1 (C) 2 (D) 5

Last Answer : (A) 0.5

If two capillary tubes of dia 0.5 mm and 1 mm are dipped in a pot containing mercury, then the rise of mercury is (A) Same in both the tubes (B) Greater in 1 mm dia tube (C) Greater in 0.5 mm dia tube (D) Zero in both the tubes

Description : If two capillary tubes of dia 0.5 mm and 1 mm are dipped in a pot containing mercury, then the rise of mercury is (A) Same in both the tubes (B) Greater in 1 mm dia tube (C) Greater in 0.5 mm dia tube (D) Zero in both the tubes

Last Answer : (C) Greater in 0.5 mm dia tube

A fluid (µ/ρ) = 0.01 cm2 /sec is moving at critical flow condition (NRe = 2100) through a pipe of dia 3 cms. Velocity of flow is __________ cm/sec. (A) 7 (B) 700 (C) 7000 (D) 630

Description : A fluid (µ/ρ) = 0.01 cm2 /sec is moving at critical flow condition (NRe = 2100) through a pipe of dia 3 cms. Velocity of flow is __________ cm/sec. (A) 7 (B) 700 (C) 7000 (D) 630

Last Answer : (A) 7

Two small diameter 10gm dielectric balls can slide freely on a vertical channel. Each carry a negative charge of 1μC. Find the separation between the balls if the lower ball is restrained from moving. a) 0.5 b) 0.4 c) 0.3 d) 0.2

Description : Two small diameter 10gm dielectric balls can slide freely on a vertical channel. Each carry a negative charge of 1μC. Find the separation between the balls if the lower ball is restrained from moving. a) 0.5 b) 0.4 c) 0.3 d) 0.2

Last Answer : c) 0.3

Harish buys petrol at rs 21, Rs.24 and Rs.27 per litre for 3 successive years. What approximately is the average cost per litre of petrol if he spends Rs.12000 each year? A) 23.74 B) 54.76 C) 24.66 D) 28.99

Description : Harish buys petrol at rs 21, Rs.24 and Rs.27 per litre for 3 successive years. What approximately is the average cost per litre of petrol if he spends Rs.12000 each year? A) 23.74 B) 54.76 C) 24.66 D) 28.99

Last Answer : A)  Total quantity of petrol consumed in 3 yr = (12000/21 +12000/24+12000/27) =12000(1/2 + 1/24 + 1/27) =12000(72+63+56/1512) =12000(191/1512) =(2292000/1512)litres Total amount spent = rs(3 *12000) = Rs.36000 Average cost = Rs(36000*1512/2292000) =Rs.23.74

The diameter of a garden roller is 1.4 m and it is 2 m long. How much area will it level in 5 revolutions? -Maths 9th

Description : The diameter of a garden roller is 1.4 m and it is 2 m long. How much area will it level in 5 revolutions? -Maths 9th

Last Answer : Radius of a garden roller (r) = 1.4 / 2 = 0.7 m and length of the garden roller (h) = 2 m ∴ Curved surface area of garden roller = 2πrh . So, the area levelled of a garden roller in one revolution is 8.8 m2. Now, area levelled of a garden in 5 revolutions = 8.8 x 5= 44m2

The diameter of a garden roller is 1.4 m and it is 2 m long. How much area will it level in 5 revolutions? -Maths 9th

Description : The diameter of a garden roller is 1.4 m and it is 2 m long. How much area will it level in 5 revolutions? -Maths 9th

Last Answer : Radius of a garden roller (r) = 1.4 / 2 = 0.7 m and length of the garden roller (h) = 2 m ∴ Curved surface area of garden roller = 2πrh . So, the area levelled of a garden roller in one revolution is 8.8 m2. Now, area levelled of a garden in 5 revolutions = 8.8 x 5= 44m2

The length of the countersunk head rivet shank is, when L = length of the rivet, G = length of grip in mm; D = Dia of rivet in mm a) L =G +0.5 D + 1mm for every 4 mm of grip or part thereof * b) b) L =G +0.5 D + 1mm c) L =G +0.5 D d) None of the above

Description : The length of the countersunk head rivet shank is, when L = length of the rivet, G = length of grip in mm; D = Dia of rivet in mm a) L =G +0.5 D + 1mm for every 4 mm of grip or part thereof * b) b) L =G +0.5 D + 1mm c) L =G +0.5 D d) None of the above

Last Answer : a) L =G +0.5 D + 1mm for every 4 mm of grip or part thereof *

he length of the snap head rivet shank is, when L = length of the rivet, G = length of grip in mm; D = Dia of rivet in mm a) L =G +1.5 D + 1mm for every 4 mm of grip or part thereof * b) b) L =G +0.5 D + 1mm c) L =G +0.5 D d) None of the above

Description : he length of the snap head rivet shank is, when L = length of the rivet, G = length of grip in mm; D = Dia of rivet in mm a) L =G +1.5 D + 1mm for every 4 mm of grip or part thereof * b) b) L =G +0.5 D + 1mm c) L =G +0.5 D d) None of the above

Last Answer : a) L =G +1.5 D + 1mm for every 4 mm of grip or part thereof *

If diameter of a wheel is 1.26 m, what the distance covered in 500 revolutions? (a) 1.38 km (b) 4.64 km (c) 2.46 km (d) 1.98 km

Description : If diameter of a wheel is 1.26 m, what the distance covered in 500 revolutions? (a) 1.38 km (b) 4.64 km (c) 2.46 km (d) 1.98 km

Last Answer : (d) 1.98 km

Given the symbols A, B, C, D, E, F, G and H with the probabilities 1/30, 1/30, 1/30, 2/30, 3/30, 5/30, 5/30 and 12/30 respectively. The average Huffman code size in bits per symbol is: (A) 67/30 (B) 70/34 (C) 76/30 (D) 78/30

Description : Given the symbols A, B, C, D, E, F, G and H with the probabilities 1/30, 1/30, 1/30, 2/30, 3/30, 5/30, 5/30 and 12/30 respectively. The average Huffman code size in bits per symbol is: (A) 67/30 (B) 70/34 (C) 76/30 (D) 78/30

Last Answer : (C) 76/30

In a hydrogen atom, the electron makes about `0.6xx10^(16)` revolutions per second around the nucleus. Determine the average current at any point on t

Description : In a hydrogen atom, the electron makes about `0.6xx10^(16)` revolutions per second around the nucleus. Determine the average current at any point on t

Last Answer : In a hydrogen atom, the electron makes about `0.6xx10^(16)` revolutions per second around the nucleus. ... at any point on the orbit of the electron.

Hazen’s formula VS = 418 (GS – Gw)d [(3T + 70)/100] is used for the settlement velocity of the particles of diameter A. Less than 0.01 mm B. Less than 0.05 mm C. Less than 0.1 mm D. Greater than 0.1 mm

Description : Hazen’s formula VS = 418 (GS – Gw)d [(3T + 70)/100] is used for the settlement velocity of the particles of diameter A. Less than 0.01 mm B. Less than 0.05 mm C. Less than 0.1 mm D. Greater than 0.1 mm

Last Answer : ANS: D

A student measured the diameter of a small steel ball using a screw gauge of least count 0.001 cm. The main scale reading is 5 mm and zero of circular

Description : A student measured the diameter of a small steel ball using a screw gauge of least count 0.001 cm. The main scale reading is 5 mm and zero of circular

Last Answer : A student measured the diameter of a small steel ball using a screw gauge of least count 0.001 cm. The main scale ... (C) 0.053 cm (D) 0.529 cm

Energy requirement (per unit mass of material crushed/ground) is highest for (A) Jaw crusher (B) Rod mill (C) Ball mill (D) Fluid energy mil

Description : Energy requirement (per unit mass of material crushed/ground) is highest for (A) Jaw crusher (B) Rod mill (C) Ball mill (D) Fluid energy mil

Last Answer : (D) Fluid energy mil

The energy consumed by a ball mill depends on (A) Its speed (B) Its ball load (C) The density of the material being ground (D) All (A), (B) and (C)

Description : The energy consumed by a ball mill depends on (A) Its speed (B) Its ball load (C) The density of the material being ground (D) All (A), (B) and (C)

Last Answer : (D) All (A), (B) and (C)

Water flow to a terminal 3 mm diameter and has an average speed of 2 m/s. What is the rate of flow in cubic meter/mm?  a. 0.0001m³/min  b. 0.076 m³/min  c. 0.085 m³/min  d. 0.097 m³/min

Description : Water flow to a terminal 3 mm diameter and has an average speed of 2 m/s. What is the rate of flow in cubic meter/mm?  a. 0.0001m³/min  b. 0.076 m³/min  c. 0.085 m³/min  d. 0.097 m³/min

Last Answer : 0.085 m³/min

A flywheel rotating at 5 revolutions per second is brought to rest by a constant torque in 10 seconds. How many revolutions does the flywheel make while coming to a stop? w) 25 x) 50 y) 75 z) 100

Description : A flywheel rotating at 5 revolutions per second is brought to rest by a constant torque in 10 seconds. How many revolutions does the flywheel make while coming to a stop? w) 25 x) 50 y) 75 z) 100

Last Answer : ANSWER: W -- 25

For a critical angle of 60 degree and the refractive index of the first medium is 1.732, the refractive index of the second medium is a) 1 b) 1.5 c) 2 d) 1.66

Description : For a critical angle of 60 degree and the refractive index of the first medium is 1.732, the refractive index of the second medium is a) 1 b) 1.5 c) 2 d) 1.66

Last Answer : b) 1.5

In a residential colony, sewers of diameters 100 mm, 150 mm and 225 mm were laid with a gradient 1 in 120. Which portion of the sewage system does not choke in due course of time? A. 100 mm dia. B. 150 mm dia. C. 225 mm dia. D. All of these

Description : In a residential colony, sewers of diameters 100 mm, 150 mm and 225 mm were laid with a gradient 1 in 120. Which portion of the sewage system does not choke in due course of time? A. 100 mm dia. B. 150 mm dia. C. 225 mm dia. D. All of these

Last Answer : ANS: C

For high level flush the nominal dia of flush pipe shall be (a) 32 mm* (b) 40 mm (c) 25 mm (d) None of these

Description : For high level flush the nominal dia of flush pipe shall be (a) 32 mm* (b) 40 mm (c) 25 mm (d) None of these

Last Answer : a) 32 mm*