Who can solve tis?
2007-03-24 4:18 pm
A uniform pole PQ of mass 50kg and length 5m is supported by two men at its end. If two masses of 80kg and 45kg are hung from two points R and S which are 1m and 1.5m from P and Q respectively. Calculate the weight supported by each men?
回答 (3)
2007-03-25 1:09 am
✔ 最佳答案
1. draw a simple force diagram: vertical downward forces:
- due to wt of rod
- 2 other due to wt of the other two hanging objects
vertical upward forces:
- 2 forces due to the lifting forces of the two men
2. Take moments at P (one end of the rod). Since the system is in equilibrium, the total moments = 0. This give you an equation containing all the downward forces and one lifting force (because moment due to lifting force at P =0). So you can readily find the lifting force at the other end Q.
3. Repeat (2) by taking moments at Q.
2007-03-25 1:12 am
You know that the total weight supported by the two men is the mass of the pole plus the mass of the two weights:50 + 80 + 45 kg = 175 kg.
As the men are each at an end of the pole, each supports half the weight of the pole.
If the two masses were suspended from the middle of the pole then each man would be supporting half the weight of the masses. (I'm assuming that the pole is level and that one man is at each end.)
The 80 kg weight is supported from a point which is closer to the man at P, so he is supporting more of its weight than is the man at Q. How much more? It's proportional to the distance from the weight to each man. As the weight is 80% of the way from Q to P, P is supporting 80% of its weight and Q is supporting 20% of its weight. Use the same technique to work out how much of the 45kg weight is supported by the man at Q, and then check your work to make sure that the total supported weights add up to 175 kg. Good luck!
As the men are each at an end of the pole, each supports half the weight of the pole.
If the two masses were suspended from the middle of the pole then each man would be supporting half the weight of the masses. (I'm assuming that the pole is level and that one man is at each end.)
The 80 kg weight is supported from a point which is closer to the man at P, so he is supporting more of its weight than is the man at Q. How much more? It's proportional to the distance from the weight to each man. As the weight is 80% of the way from Q to P, P is supporting 80% of its weight and Q is supporting 20% of its weight. Use the same technique to work out how much of the 45kg weight is supported by the man at Q, and then check your work to make sure that the total supported weights add up to 175 kg. Good luck!
2007-03-25 1:10 am
wt taken by person atp=102.5g N and at q=72.5g N.
just consider summation v=0 and summation m=0.
just consider summation v=0 and summation m=0.
收錄日期: 2021-05-03 05:08:03
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070324081809AAhuGJs