When you try to solve problems of Physics in general and of application of Newton’s laws in particular, it is important to **follow a certain order**. Try to be organized when you solve these problems, and you will see how it gives good results. It is worth spending a bit of time on the analysis of a problem before tackling it.

When solving problems related to the application of Newton’s laws, follow these steps:

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- Read carefully the problem statement.
- Draw a picture of the physical situation described in the problem.
- Write in your notebook the givens of the problem statement.
- Identify the forces that act on the body.
- Remember that the forces are physical interactions. Therefore, if a system is supported on another system, a normal force will act on it; if it is close to the surface of the Earth, the weight will act on it, and so on with the rest of the interactions that the system experiences.
- Represent the different forces acting on the body on the drawing you have made.
- Add a Cartesian coordinate system on the drawing,
**indicating which is the positive direction of each of the axes**. - Write
**Newton’s second law in vectorial form**, including in the vectorial sum all the forces you have identified. - Project Newton’s second law on Cartesian axes. Take into account the sign of the different projections.
- Solve the system of equations to determine the unknowns.
- Do not forget to
**include the units**in your results. - Review the problem and check that the results you have obtained make sense.

On the following pages you will find some problems of Newton’s second law with solutions. **Try to do them before looking at the solution**.