ACA COMPREHENSIVE ANSWERS AND QUESTIONS
SET A+
✔✔Determine the maximum total head at which a 5 hp centrifugal pump can extract
water at a rate of 25 lps if pump efficiency is 65%. - ✔✔Answer: 32.48ft
✔✔What is the run-off coefficient for a 576-ha watershed if the peak runoff rate for a
0.80 cm/hr rainfall intensity is 3.25 m3/sec? - ✔✔Answer: 0.25
✔✔How many sprinklers with spacing of 7m x 7m are needed to irrigate a rectangular
piece of land 125 m x 190m if the laterals are set parallel to the longer side of the field?
- ✔✔Answer: 486
✔✔Under a perfect competition, a firm can sell at a price of P200 per unit all of a
particular commodity it produces. If C(X) pesos is the total cost of each day's production
when x units are produced, and C(x) = 2x2 + 40x + 1400, find the number of units that
should be produced daily for the firm to have the greatest daily total profit. - ✔✔Answer:
40
✔✔The required diameter of a sprinkler to be operated at an average pressure of 50psi
at a discharge of 6.34gpm assuming a discharge coefficient of 0.965 is. - ✔✔Answer:
3/16"
✔✔If the impeller speed of a centrifugal pump is increased from 1800 rpm to 2340 rpm,
the resulting power will be how many times the original? - ✔✔Answer: 2.197
✔✔A sprinkler irrigation system is to be operated at an average pressure of 40psi. The
friction losses along the lateral running uphill amount to 16.5ft. If the elevation difference
between the first and last sprinkler is 3ft and the riser heights is 4ft, the required inlet
pressure at the lateral is. - ✔✔Answer: 48psi
, ✔✔Find the depth of a trapezoidal open channel to carry 300 cfs assuming a bottom
width of 4.5 ft, a slope of 0.08%, a side slope of 2:1, freeboard of 20%, and a clean,
straight channel with no rifts (n=0.03). - ✔✔Answer: 6.0 ft
✔✔What is the void ratio for a soil with apparent specific gravity and real specific gravity
of 1.15 and 2.35, respectively? - ✔✔Answer: 1.04
✔✔The field needs the application of 65 kg of N per hectare (60-0-0). Nitrogen can be
supplied by either urea (45-0-0) or ammonium sulfate (21-0- 0), each bag of which
weighs 50 kg. If the field measures 3 hectares, how many bags of urea are needed? -
✔✔Answer: 9
✔✔Compute for the brake horsepower of a pump needed to pump-out a fluid (_=1.3
g/cc) at a rate of 300 gpm with a total head of 6m. assume pump efficiency of 60%. -
✔✔Answer: 3.5 hp
✔✔A 16-ft thick confined aquifer with hydraulic conductivity of 500ft/day was tapped by
a 4" shallow tubewell. With a radius of influence of 2000 ft, determine the maximum
discharge of the STW in liters per second. Assume an allowable drawdown of 10 ft. -
✔✔Answer: 17.55
✔✔Given a shallow tubewell with maximum discharge of 15 lps and a total dynamic
head of 7 meters. Determine the power rating of the primemover for the pump if pump
and primemover efficiencies are 60 and 55 % respectively. - ✔✔Answer: 4Hp
✔✔What is the discharge in each sprinkler nozzle to irrigate a rectangular piece of land
150m x 180m if the laterals are set parallel to the longer side of the field. Sprinkler
spacing is 6m x 6m, irrigation water requirement is 150mm and irrigation period is 6
hours. - ✔✔Answer: 0.250 lps
✔✔If all sacks of rice distributed by a local retailer have a mean weight of 50 kilograms
with a standard deviation of 0.02 kilograms, at least what percentage of the sacks must
contain between 49.95 and 50.05 kilograms of rice? - ✔✔Answer: 84%
✔✔The effective rainfall during the month of May is 120 mm. On a certain farm with an
area of 12.355 acres, the consumptive use was 9 mm/day. If 10,000 m3 of water was
used to irrigate the farm, what is the irrigation efficiency? - ✔✔Answer: 79.5%
✔✔A soil sample was obtained using a cylindrical soil sampler with a 4" diameter and
10" height. After oven drying, the sample weighed 2,470 grams. What is the soil's bulk
density? - ✔✔Answer: 1200kg/m3
SET A+
✔✔Determine the maximum total head at which a 5 hp centrifugal pump can extract
water at a rate of 25 lps if pump efficiency is 65%. - ✔✔Answer: 32.48ft
✔✔What is the run-off coefficient for a 576-ha watershed if the peak runoff rate for a
0.80 cm/hr rainfall intensity is 3.25 m3/sec? - ✔✔Answer: 0.25
✔✔How many sprinklers with spacing of 7m x 7m are needed to irrigate a rectangular
piece of land 125 m x 190m if the laterals are set parallel to the longer side of the field?
- ✔✔Answer: 486
✔✔Under a perfect competition, a firm can sell at a price of P200 per unit all of a
particular commodity it produces. If C(X) pesos is the total cost of each day's production
when x units are produced, and C(x) = 2x2 + 40x + 1400, find the number of units that
should be produced daily for the firm to have the greatest daily total profit. - ✔✔Answer:
40
✔✔The required diameter of a sprinkler to be operated at an average pressure of 50psi
at a discharge of 6.34gpm assuming a discharge coefficient of 0.965 is. - ✔✔Answer:
3/16"
✔✔If the impeller speed of a centrifugal pump is increased from 1800 rpm to 2340 rpm,
the resulting power will be how many times the original? - ✔✔Answer: 2.197
✔✔A sprinkler irrigation system is to be operated at an average pressure of 40psi. The
friction losses along the lateral running uphill amount to 16.5ft. If the elevation difference
between the first and last sprinkler is 3ft and the riser heights is 4ft, the required inlet
pressure at the lateral is. - ✔✔Answer: 48psi
, ✔✔Find the depth of a trapezoidal open channel to carry 300 cfs assuming a bottom
width of 4.5 ft, a slope of 0.08%, a side slope of 2:1, freeboard of 20%, and a clean,
straight channel with no rifts (n=0.03). - ✔✔Answer: 6.0 ft
✔✔What is the void ratio for a soil with apparent specific gravity and real specific gravity
of 1.15 and 2.35, respectively? - ✔✔Answer: 1.04
✔✔The field needs the application of 65 kg of N per hectare (60-0-0). Nitrogen can be
supplied by either urea (45-0-0) or ammonium sulfate (21-0- 0), each bag of which
weighs 50 kg. If the field measures 3 hectares, how many bags of urea are needed? -
✔✔Answer: 9
✔✔Compute for the brake horsepower of a pump needed to pump-out a fluid (_=1.3
g/cc) at a rate of 300 gpm with a total head of 6m. assume pump efficiency of 60%. -
✔✔Answer: 3.5 hp
✔✔A 16-ft thick confined aquifer with hydraulic conductivity of 500ft/day was tapped by
a 4" shallow tubewell. With a radius of influence of 2000 ft, determine the maximum
discharge of the STW in liters per second. Assume an allowable drawdown of 10 ft. -
✔✔Answer: 17.55
✔✔Given a shallow tubewell with maximum discharge of 15 lps and a total dynamic
head of 7 meters. Determine the power rating of the primemover for the pump if pump
and primemover efficiencies are 60 and 55 % respectively. - ✔✔Answer: 4Hp
✔✔What is the discharge in each sprinkler nozzle to irrigate a rectangular piece of land
150m x 180m if the laterals are set parallel to the longer side of the field. Sprinkler
spacing is 6m x 6m, irrigation water requirement is 150mm and irrigation period is 6
hours. - ✔✔Answer: 0.250 lps
✔✔If all sacks of rice distributed by a local retailer have a mean weight of 50 kilograms
with a standard deviation of 0.02 kilograms, at least what percentage of the sacks must
contain between 49.95 and 50.05 kilograms of rice? - ✔✔Answer: 84%
✔✔The effective rainfall during the month of May is 120 mm. On a certain farm with an
area of 12.355 acres, the consumptive use was 9 mm/day. If 10,000 m3 of water was
used to irrigate the farm, what is the irrigation efficiency? - ✔✔Answer: 79.5%
✔✔A soil sample was obtained using a cylindrical soil sampler with a 4" diameter and
10" height. After oven drying, the sample weighed 2,470 grams. What is the soil's bulk
density? - ✔✔Answer: 1200kg/m3
