9.4: Problem solving steps
We’ll follow the same problem-solving steps as with problems dealing with conservation laws, but this time we’ll add an intermediate step between the drawing and the math:
- Draw a picture.
- Using your picture, draw a free body diagram that represents the forces acting on one particular object.
- Using your free body diagram, apply Newton’s second law.
- Solve.
A free body diagram (FBD) is a problem-solving tool that we’ll use to bridge the gap between the very visual and intuitive picture, and the more abstract mathematical representation. To draw a free body diagram, represent your object as a single point, then draw arrows coming from that point that represent the different forces acting on that particular object. You also need to include coordinate axes for reference.
Example
Practice
9.5 Mechanical equilibrium
An object (or group of objects) is said to be in mechanical equilibrium when the net force on it is zero. You could also describe this in terms of an object’s motion, considering Newton’s second law: an object is in mechanical equilibrium when it is not accelerating.
This describes many things that we encounter in the world around us. For example, take a look at any building—if any piece of a building has an acceleration other than zero, you do not want to be in or near that building!