We list for you five important tips to help you solve Physics exercises. Do not fool yourself! There is no magic to resolve issues, in fact, it takes a lot of study and dedication. However, if you have difficulty with this discipline, there are some important steps that can make solving the exercises simpler. Check out!
I. Know the theory!
Physics is a science that has very rich theories and very well elaborated by several icons of this science. Trying to solve a physics exercise without knowing the theory that explains the phenomenon in question can be the right way to go wrong.
Let's think about the example of Geometrical Optics, in which the spherical mirrors are studied. In the analytical study of spherical mirrors, it is defined that the focus of the convex mirror is negative and the focus of the concave mirror is positive. Someone who doesn't know this detail, but only has the Gauss equation (an equation that relates the object and image positions with the mirror focus), could make mistakes at the time of put the positive or negative signs in the values of the equation or it would not know how to interpret an answer that indicated a negative value for the focus of a mirror, recognizing it as convex, by example.
II. Write down the data!
Throughout the enunciation of the questions, the necessary data for their resolution are provided. It is extremely important to list the data provided in order to have everything that will be needed to resolve the issue in an accessible way. If the data is not listed, whenever the need for its use arises, you will have to read the statement again and look for the desired information. This can cause you to get lost in the exercise resolution.
III. Identify the question!
All exercises have something called a question command, which is precisely the exercise question, what should you find. It is very important that the command of the issue is very clear and understood, as only then the paths to the resolution can be found.
IV. Check the measurement units!
Know the determinations of the International System of Units (SI) is very important in solving exercises, as the final answer will only be correct if the measurement units are used correctly.
Imagine an exercise in which you must determine the net force acting on a 500 g object so that it has an acceleration equal to 10 m/s2. In this case, transform the object's mass from gram (g) to kilogram (kg), since the unit of force (N – newton) is defined in terms of kg, not g. Therefore, the value to be used for the mass is 0.5 kg. Check the resolution:
From the Newton's Second Law, we have:
FR = m.a
FR = 0,5. 10
FR = 5 N
V. analyze the equations
After annotating the data, understand the command of the question and place all the units of measure according to the International System, one must look in the theory for which or which equations can be used to solve the problem. There are cases where more than one equation can be used. When that happens, choose the simplest path.
Example
Let's solve the exercise below by following all five tips given above.
Determine the amount of heat needed to raise from 20°C to 100°C a 400 g iron pan that has a specific heat of 450 J/Kg°C
1. Theory involved
Amount of heat; calorimetry.
2. Question data
Pasta: m = 400 g
initial temperature = 20°C
final temperature = 100 °C
Temperature variation: ΔT = 100 – 20 = 80°C
specific heat of iron: c = 450 J/Kg°C
3. question command
Determine the amount of heat that will be supplied to the iron so that its temperature rises from 20°C to 100°C.
4. checking the units
The specific heat of iron was given based on the units of joule (J), kilogram (kg) and degrees Celsius (°C). As the pot's mass was given in grams, it must be converted to kilograms.
Mass: m = 400g ÷ 1000 = 0.4 Kg
5. Equation
The equation to be used is the one that determines the amount of sensible heat supplied or removed from a body.
Q = m.c.ΔT
Q = amount of heat;
m = mass;
c = specific heat;
ΔT = temperature variation.
Resolution:
Q = m.c.ΔT
Q = 0.4. 450. 80
Q = 14,400 J
It will take 14,400 J of heat to heat the iron pan from 20°C to 100°C.
By Joab Silas
Graduated in Physics
Source: Brazil School - https://brasilescola.uol.com.br/fisica/cinco-dicas-para-resolver-exercicios-fisica.htm