03 2-1 (c) The resultant of two unlike parallel forces
Rule
- Let act in opposite directions at and .
- The resultant is parallel to them, in the direction of the larger force, with magnitude
- Its line of action cuts at a point outside the segment, on the side of the larger force, and
- Here is again nearer to the larger force .
- If there is no resultant force: the pair is a couple (see the next lesson).
✍️ Worked examples
Example 3: Unlike forces of 100 N (at ) and 40 N (at ) act at points 240 cm apart. Find the resultant.
Solution:
- N in the direction of the 100 N force.
- lies on produced beyond , with .
- , so and cm.
- The resultant acts 160 cm from outside the segment .