resultant forces

what is resultant force

the single force that has the same effect as all of the original forces acting together

(spec definition) -A number of forces acting on an object may be replaced by a single force that has the same effect as all the original forces acting together. This single force is called the resultant force.

free-body diagram

the object is shown as a point and the forces are drawn as arrow starting at the point and the length of the arrow will show the size of the force

how to answer following question:

two forces are acting on an object. One force has a magnitude of 10 N and the other force has a magnitude of 8 N. The angle between the two forces is 30 degrees. Calculate the resultant force

1. make a scale drawing showing the forces involved eg 1cm : 1N

2. using ruler draw a 10cm line from single dot, which will represent object

3. using protractor, we measure an angle of 30 degrees

4. use ruler again to draw a 8cm arrow to represent the 8 N force

5. now we need to draw parallelogram, to do that we coly the 8cm. line and position it at the head of the 10cm force vector and we should also use a protractor to double check that the angle is still 30 degrees

6. now copy 10cm line and position it at the head of the 8 cm force vector

7. draw a line from the tails of the force vector to the other side of the parallelogram

8. we measure the length of the vector and work out the resultant force that it represents

tg

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