| Author | Message | ||
     Lau Kai Kwong Username: lkk Registered: 04-2003 |
A uniform bar AB of 1m long can be balanced about a point 0.2m from A by hanging a weight of 6N at A. Find the weight of the bar. | ||
| 971076 Username: 971076 Registered: 04-2003 |
6N *0.2 = 0.3 * M M = 4N Let M be the force of the uniform bar at the middle of AB | ||
| Lau Kai Kwong Username: lkk Registered: 04-2003 |
M is always used as the symbol of mass, so you would better define the weight as W. Besides, you would better: 1. write the definition first; 2. not to write 0.3 directly, write the steps how you get 0.3; 3. write down how can you get the equation. For example, by taking moment at the point 0.2m from A. | ||
| Lau Kai Kwong Username: lkk Registered: 04-2003 |
Further, you would better draw a force diagram. | ||
| 971076 Username: 971076 Registered: 04-2003 |
since AB is 1m, so the middle part is 0.5m Let the middle point be C then the length between 0.2m from A and C is 0.3m Let W be the weight of uniform bar by taking the moment on 0.2m from A 6N*0.2=0.3*W W=4N | ||
| Lau Kai Kwong Username: lkk Registered: 04-2003 |
You can draw a diagram to show how you get 0.3m instead. |