# solving physics problems

I am the only “pure” physics tutor – the rest of the tutors are mathematicians or engineers who feel very comfortable with mathematics (justly so, they’re all quite awesome).  - If you place your answer back into the equation which you were using to solve the problem and it gives the correct given values, then this does not necessarily mean that you have found the correct answer. Comments: First you want to model the body, in one of three ways: What to include: Since a free body diagram represents the body itself and the external forces on it. Examples: After having done the math in the solution stage of problem solving, it is tempting to think you are done. If you do not practice solving equations, then it becomes much harder to manipulate the relevant generic equations to generate an equation that you can put into your calculator to solve in the first place. In most physics problems, there is more than one way to reach a solution, often meaning that more than one equation can work. Dimensional analysis is the practice of checking relations between physical quantities by identifying their dimensions. Examples: Each variable in a generic equation is a pointer to a concept. - There may be other quantities that are not requested that may need to be both symbolized and found before the requested unknown can be found. It’s like a puzzle, and the more you do it, the better you get at it. Is my answer reasonable? From what frame of reference shall I choose to observe the action described? If you’re trying to find out how fast a ball rolling down a curved ramp (without slipping and air resistance) is going at the bottom of the ramp using forces and torques, you will have to do a path integral of the force, which changes depending on the position, so good luck. I wrote all the example problems based on the techniques and guidelines described. Trigonometry is also used in determining the horizontal and vertical components of forces and objects. For example, getting a visual idea of your frame of reference, or of the difference between up (positive) and down (negative), can mean the difference between a right answer and a wrong one. Sunil Kumar Singh, Free Body Diagram (Application). We reject the v2 = 0 solution because we know v2 is not zero, so we’re left with the other solution. Normally, directions to the right are taken to be positive as are directions upwards. Reflective Mental Overseer Questions: Water flows through a constriction in a pipe. The following equation can be used to find the conversion factor between the two derived dimensions: ${\text{n}_2=\frac{\text{u}_2}{\text{u}_1}*\text{n}_1}$. Objects only need to be simple symbolic representations - the simpler the better. Comment: If the acceleration of the box is 3.5 m/s^2 (and friction can be neglected) at what angle to the horizontal does the man pull? The ball is observed to hit the ground 15.0 m from the base of the building, .420 seconds after it is launched. Organize your formulas in front of you. The first equation comes from the fact that cos(θ) has a zero at 1/2 π (90 degrees) and repeats every integer multiple of π (180 degrees), which is what the right-hand side of the first equation means (1/2 π plus some integer multiple of π). Before the collision, the first ball moves at velocity vi. - The symbols with which you tag an unknown may be personal to you. The bottom line in any symbolic solution is to arrive at an equation that looks like Some questions already come with a drawing – use it! Likewise, the larger radius means a higher moment of inertia, but since there is no slipping, the angular velocity, velocity, and radius are constrained in such a way that the rotational kinetic energy is independent of the radius. (A) What was the car's acceleration while braking ? Dimensional analysis is based on the fact that physical law must be independent of the units used to measure the physical variables.