標題:
PHY 天同help 20點
發問:
1. consider a lift car is lifted by a motor with strings wounding around the drum which is connected to the motor . Explain why frictional drum surface is necessaryfor the lifting 2. assume the bulb under rated value is 20W only 15 W turns to light energy so the energy output is 15w or 20 w?thx!! 顯示更多 1. consider a lift car is lifted by a motor with strings wounding around the drum which is connected to the motor . Explain why frictional drum surface is necessary for the lifting 2. assume the bulb under rated value is 20W only 15 W turns to light energy so the energy output is 15w or 20 w? thx!!
1. Friction is required on the drum to prevent slipping of the car cable. Otherwise, there is no force to lift the cable and the car even the drum is rotated by the motor. 2. The term "energy output" generally refers to the "useful energy output". In the case of a light bulb, the useful energy output is light. Thus the output power should be 15 w. Having said that, I presume the figure "15 w" for energy output of a 20 w bulb is only hypothetical. In reality, the efficacy of a light bulb shall not be so high.
其他解答:
1. As the requirement to lift/move the lift car through the motor rotation of the drum, the net force exerted on the strings must equal to greater than the weight of the lift car in order to move, so the frictional drum surface is required to produce equal and opposite force as the motor rotates the drum such that the frictional force on the drum may transfer as the pulling force on the strings. 2. By definition of energy output is the energy/power use as the intended work, light in this case. So the output power(or energy) is 15W. The input power may be the "rated" power 20W. So about 5W is lost or spent on components of the bulb to create the light, such as the electronic driver, transformer, controls, wiring.|||||1. friction is not important as long as the string was tighten up to the drum, but everything has friction, you need not specify a frictional drum. 2. still 20W as 5W is heat engery.
PHY 天同help 20點
發問:
1. consider a lift car is lifted by a motor with strings wounding around the drum which is connected to the motor . Explain why frictional drum surface is necessaryfor the lifting 2. assume the bulb under rated value is 20W only 15 W turns to light energy so the energy output is 15w or 20 w?thx!! 顯示更多 1. consider a lift car is lifted by a motor with strings wounding around the drum which is connected to the motor . Explain why frictional drum surface is necessary for the lifting 2. assume the bulb under rated value is 20W only 15 W turns to light energy so the energy output is 15w or 20 w? thx!!
此文章來自奇摩知識+如有不便請留言告知
最佳解答:1. Friction is required on the drum to prevent slipping of the car cable. Otherwise, there is no force to lift the cable and the car even the drum is rotated by the motor. 2. The term "energy output" generally refers to the "useful energy output". In the case of a light bulb, the useful energy output is light. Thus the output power should be 15 w. Having said that, I presume the figure "15 w" for energy output of a 20 w bulb is only hypothetical. In reality, the efficacy of a light bulb shall not be so high.
其他解答:
1. As the requirement to lift/move the lift car through the motor rotation of the drum, the net force exerted on the strings must equal to greater than the weight of the lift car in order to move, so the frictional drum surface is required to produce equal and opposite force as the motor rotates the drum such that the frictional force on the drum may transfer as the pulling force on the strings. 2. By definition of energy output is the energy/power use as the intended work, light in this case. So the output power(or energy) is 15W. The input power may be the "rated" power 20W. So about 5W is lost or spent on components of the bulb to create the light, such as the electronic driver, transformer, controls, wiring.|||||1. friction is not important as long as the string was tighten up to the drum, but everything has friction, you need not specify a frictional drum. 2. still 20W as 5W is heat engery.
文章標籤
全站熱搜
留言列表
