#### Physics problem solving

At the same time to understand physics we need to solve as many physics problems as possible. Only by solving physics problems can we understand Physics Laws and how to apply them.

There are a few general rules we need to follow when we solve Physics Problems. These rules are. Another important fact about Physics Problems is knowing how to read the Solution to a Physics Problem:. It is very important to understand the solution of the problem when you read it in the book. You read the solution of the problem and it looks very simple, so you think you understand it. But you could be wrong.

To find out if you understand the solution of the problem or not you need to close the book and try to solve the problem by yourself.

If you can solve the problem then you understand the solution. If not then you need to open the book and read the solution again, then close the book and try to solve the problem again. It is very important that you are able to solve physics problems without looking at the solutions. Contact us. All rights reserved. Free problems. Conservation laws. Fluids and elasticity. Ideal gas. AC current. Free problems :.Problem-solving skills are clearly essential to success in a quantitative course in physics.

More important, the ability to apply broad physical principles—usually represented by equations—to specific situations is a very powerful form of knowledge.

It is much more powerful than memorizing a list of facts. Analytical skills and problem-solving abilities can be applied to new situations whereas a list of facts cannot be made long enough to contain every possible circumstance.

Such analytical skills are useful both for solving problems in this text and for applying physics in everyday life. As you are probably well aware, a certain amount of creativity and insight is required to solve problems. No rigid procedure works every time.

Creativity and insight grow with experience. With practice, the basics of problem solving become almost automatic.

### 1.8: Solving Problems in Physics

Another is to work as many end-of-section problems as possible, starting with the easiest to build confidence and then progressing to the more difficult. After you become involved in physics, you will see it all around you, and you can begin to apply it to situations you encounter outside the classroom, just as is done in many of the applications in this text.

Although there is no simple step-by-step method that works for every problem, the following three-stage process facilitates problem solving and makes it more meaningful. The three stages are strategy, solution, and significance. This process is used in examples throughout the book. Here, we look at each stage of the process in turn. Strategy is the beginning stage of solving a problem. The idea is to figure out exactly what the problem is and then develop a strategy for solving it.

Some general advice for this stage is as follows:. The solution stage is when you do the math. Substitute the knowns along with their units into the appropriate equation and obtain numerical solutions complete with units. That is, do the algebra, calculus, geometry, or arithmetic necessary to find the unknown from the knowns, being sure to carry the units through the calculations.

This step is clearly important because it produces the numerical answer, along with its units. Notice, however, that this stage is only one-third of the overall problem-solving process. After having done the math in the solution stage of problem solving, it is tempting to think you are done.

But, always remember that physics is not math. Rather, in doing physics, we use mathematics as a tool to help us understand nature. So, after you obtain a numerical answer, you should always assess its significance:.Success in problem solving is obviously necessary to understand and apply physical principles, not to mention the more immediate need of passing exams. These techniques also reinforce concepts that are useful in many other areas of physics.

Many problem-solving strategies are stated outright in the worked examples, and so the following techniques should reinforce skills you have already begun to develop. Step 1. As usual, it is first necessary to identify the physical principles involved. Such a sketch is shown in Figure 1 a. Then, as in Figure 1 buse arrows to represent all forces, label them carefully, and make their lengths and directions correspond to the forces they represent whenever sufficient information exists.

Figure 1. T is the tension in the vine above Tarzan, F T is the force he exerts on the vine, and w is his weight. All other forces, such as the nudge of a breeze, are assumed negligible. We then define the system of interest as shown and draw a free-body diagram. Step 2. Identify what needs to be determined and what is known or can be inferred from the problem as stated. That is, make a list of knowns and unknowns. Then carefully determine the system of interest. See Figure 1 c. As illustrated earlier in this chapter, the system of interest depends on what question we need to answer. This choice becomes easier with practice, eventually developing into an almost unconscious process. Skill in clearly defining systems will be beneficial in later chapters as well.

A diagram showing the system of interest and all of the external forces is called a free-body diagram. Only forces are shown on free-body diagrams, not acceleration or velocity. We have drawn several of these in worked examples. Figure 1 c shows a free-body diagram for the system of interest. Note that no internal forces are shown in a free-body diagram.Login or Register Physics Review Online doctor.

Random tutorial video notice how the solver shows step-by-step work Show me more video tutorials and practice questions. Available solvers: Please register to access them. Alpha Solver uses the following convention: Up is positive. Down is negative.

Right is positive. Left is negative. Up an incline is positive. Down an incline is negative. It's very intuitive. But if you get it wrong, then the answer will be wrong. Get your units right If the unit is in SI, then no unit is required in the input.

All non-SI units must be appended at the end of the value. For everything else, we follow the SI convention.

## 1.8: Solving Problems in Physics

When in doubt, include the units! SI temperature is K, not C.

Input is case sensitive! Eg, velocity is the same as v. Scientific notation Yes! Alpha Solver takes scientific notation for very large and very small values. Official variable list for Alpha Solver Physics First thing: Don't stress about memorizing all the variables in one go! Besides, your teacher will only teach you a few variables at a time. Note: not all variables below are available in a particular app. Some variables can mean 2 or more things.Any physical quantity can be expressed as a product of a combination of the basic physical dimensions.

The dimension of a physical quantity indicates how it relates to one of the seven basic quantities. These fundamental quantities are:.

As you can see, the symbol is enclosed in a pair of square brackets. This is often used to represent the dimension of individual basic quantity.

Dimensional analysis is the practice of checking relations between physical quantities by identifying their dimensions. The dimension of any physical quantity is the combination of the basic physical dimensions that compose it. Dimensional analysis is based on the fact that physical law must be independent of the units used to measure the physical variables. It can be used to check the plausibility of derived equations, computations and hypotheses.

The dimensions of derived quantities may include few or all dimensions in individual basic quantities. In order to understand the technique to write dimensions of a derived quantity, we consider the case of force.

Force is defined as:. The dimension of acceleration, represented as [a], is itself a derived quantity being the ratio of velocity and time. In turn, velocity is also a derived quantity, being ratio of length and time. In practice, one might need to convert from one kind of dimension to another.

For common conversions, you might already know how to convert off the top of your head. But for less common ones, it is helpful to know how to find the conversion factor:. You can then use ratios to figure out the conversion:. Trigonometry is central to the use of free body diagrams, which help visually represent difficult physics problems.

In physics, most problems are solved much more easily when a free body diagram is used. Free body diagrams use geometry and vectors to visually represent the problem. Trigonometry is also used in determining the horizontal and vertical components of forces and objects. Free body diagrams are very helpful in visually identifying which components are unknown and where the moments are applied. They can help analyze a problem, whether it is static or dynamic. When people draw free body diagrams, often not everything is perfectly parallel and perpendicular.

Sometimes people need to analyze the horizontal and vertical components of forces and object orientation. When the force or object is not acting parallel to the x or y axis, people can employ basic trigonometry to use the simplest components of the action to analyze it. Basically, everything should be considered in terms of x and ywhich sometimes takes some manipulation.

Free Body Diagram : The rod is hinged from a wall and is held with the help of a string. This exercise involves drawing the free body diagram. To make the problem easier, the force F will be expressed in terms of its horizontal and vertical components. Removing all other elements from the image helps produce the finished free body diagram.

Free Body Diagram : The free body diagram as a finished product. Given the finished free body diagram, people can use their knowledge of trigonometry and the laws of sine and cosine to mathematically and numerical represent the horizontal and vertical components:. This uses geometry and vectors to visually represent to problem, and trigonometry is also used in determining horizontal and vertical components of forces and objects.

Purpose: Free body diagrams are very helpful in visually identifying which components are unknown, where the moments are applied, and help analyze a problem, whether static or dynamic.Last Updated: August 28, References.

To create this article, 23 people, some anonymous, worked to edit and improve it over time. This article has been viewedtimes. Learn more Baffled as to where to begin with a physics problem? There is a very simply and logical flow process to solving any physics problem.

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Cookie Settings. Learn why people trust wikiHow. Download Article Explore this Article Steps. Tips and Warnings. Things You'll Need.Success in problem solving is necessary to understand and apply physical principles. These techniques also reinforce concepts that are useful in many other areas of physics. Many problem-solving strategies are stated outright in the worked examples, so the following techniques should reinforce skills you have already begun to develop.

Whenever sufficient information exists, it is best to label these arrows carefully and make the length and direction of each correspond to the represented force. All other forces, such as the nudge of a breeze, are assumed to be negligible. We then define the system of interest as shown and draw a free-body diagram. As with most problems, we next need to identify what needs to be determined and what is known or can be inferred from the problem as stated, that is, make a list of knowns and unknowns.

Only forces are shown in free-body diagrams, not acceleration or velocity. We have drawn several free-body diagrams in previous worked examples. Note that no internal forces are shown in a free-body diagram. In general, once external forces are clearly identified in free-body diagrams, it should be a straightforward task to put them into equation form and solve for the unknown, as done in all previous examples. If the problem is one-dimensional—that is, if all forces are parallel—then the forces can be handled algebraically.

If the problem is two-dimensional, then it must be broken down into a pair of one-dimensional problems. We do this by projecting the force vectors onto a set of axes chosen for convenience.

As seen in previous examples, the choice of axes can simplify the problem.

## 6.2: Solving Problems with Newton's Laws (Part 1)

For example, when an incline is involved, a set of axes with one axis parallel to the incline and one perpendicular to it is most convenient. It is almost always convenient to make one axis parallel to the direction of motion, if this is known. Then, you have the following equations:. We need this information to determine unknown forces acting on a system. As always, we must check the solution. In some cases, it is easy to tell whether the solution is reasonable.

For example, it is reasonable to find that friction causes an object to slide down an incline more slowly than when no friction exists. In practice, intuition develops gradually through problem solving; with experience, it becomes progressively easier to judge whether an answer is reasonable. Another way to check a solution is to check the units. If we are solving for force and end up with units of millimeters per second, then we have made a mistake. These serve also to illustrate some further subtleties of physics and to help build problem-solving skills. Recall that a particle in equilibrium is one for which the external forces are balanced.

Static equilibrium involves objects at rest, and dynamic equilibrium involves objects in motion without acceleration, but it is important to remember that these conditions are relative. For example, an object may be at rest when viewed from our frame of reference, but the same object would appear to be in motion when viewed by someone moving at a constant velocity. Consider the traffic light mass of Find the tension in each wire, neglecting the masses of the wires.

The free-body diagram for the traffic light is also shown. The horizontal components of the tensions must cancel, and the sum of the vertical components of the tensions must equal the weight of the traffic light.

The three forces involved are not parallel, and so they must be projected onto a coordinate system.