Some engineers have developed a device that provides lighting to rural areas with no access to grid electricity. The device is intended for indoor use. It is driven by gravity, and it works as follows: A bag of rock or sand is raised by human power to a higher location. As the bag descends very slowly, it powers a sprocket-wheel which also rotates slowly. A gear train mechanism converts this slow motion to high speed, which drives a DC generator. The electric output from the generator is used to power an LED bulb. Consider a gravity-driven LED bulb that provides 16 lumens of lighting. The device uses a 10-kg sandbag that is raised by human power to a 2-m height. For continuous lighting, the bag needs to be raised every 20 minutes. Using an efficacy of 150 lumens per watt for the LED bulb, determine ( a ) the velocity of the sandbag as it descends and ( b ) the overall efficiency of the device.
Some engineers have developed a device that provides lighting to rural areas with no access to grid electricity. The device is intended for indoor use. It is driven by gravity, and it works as follows: A bag of rock or sand is raised by human power to a higher location. As the bag descends very slowly, it powers a sprocket-wheel which also rotates slowly. A gear train mechanism converts this slow motion to high speed, which drives a DC generator. The electric output from the generator is used to power an LED bulb. Consider a gravity-driven LED bulb that provides 16 lumens of lighting. The device uses a 10-kg sandbag that is raised by human power to a 2-m height. For continuous lighting, the bag needs to be raised every 20 minutes. Using an efficacy of 150 lumens per watt for the LED bulb, determine ( a ) the velocity of the sandbag as it descends and ( b ) the overall efficiency of the device.
Some engineers have developed a device that provides lighting to rural areas with no access to grid electricity. The device is intended for indoor use. It is driven by gravity, and it works as follows: A bag of rock or sand is raised by human power to a higher location. As the bag descends very slowly, it powers a sprocket-wheel which also rotates slowly. A gear train mechanism converts this slow motion to high speed, which drives a DC generator. The electric output from the generator is used to power an LED bulb.
Consider a gravity-driven LED bulb that provides 16 lumens of lighting. The device uses a 10-kg sandbag that is raised by human power to a 2-m height. For continuous lighting, the bag needs to be raised every 20 minutes. Using an efficacy of 150 lumens per watt for the LED bulb, determine (a) the velocity of the sandbag as it descends and (b) the overall efficiency of the device.
Branch of science that deals with the stationary and moving bodies under the influence of forces.
The drive is by V-belts from an electric motor running at 1500 r.p.m. A compressor, requiring 75000W is to run at about 500 r.p.m. The diameter of the pulley on the compressor shaft must not be greater than 1.2 meter while the centre distance between the pulleys is limited to 1.85 meter. The belt speed should not exceed 1500 m/min. Determine the number of V-belts required to transmit the power if each belt has a cross-sectional area of 3 cm2, density 1100 kg/m3 and an allowable tensile stress of 3 MPa. The groove angle of the pulley is 50°. The coefficient of friction between the belt and the pulley is 0.3. Calculate also the length required of each belt.
A solar pond power plant produced power output at 350 kW and thermal efficiency of 4%.Sketch the schematic diagram of the system and determine the rate of solar energy collected.
Two parallel shafts whose centers are 10 meters apart are connected by an open belt drive
with a V-belt with a groove angle of 30°. The diameter of the larger pulley is 1000 mm and
that of the smaller pulley is 400 mm. The smaller pulley is running at 1000 rpm to deliver 10
kW of power. The mass of the belt is 1 kg/m. Taking centrifugal tension into account,
determine the minimal cross-sectional area if the allowable tensile stress of the belt is 5 MPa.
The coefficient of friction between the belt and the pulleys is 0.25.
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