O National High School Exam (Enem) is today one of the most important selection processes carried out in Brazil. It is used as a gateway to a number of universities across the country.
Regarding the contents of Physics, generally six subjects are very much explored: mechanics, undulatory, electricity, magnetism, thermology and optics. With that in mind, we selected for you the 10 equations that are part of these six subjects to help you better prepare for the Physics questions in Enem.
1) Average speed
Average speed is defined as the ratio between the total space traveled by a piece of furniture and the time spent by it.
v: average speed;
Δs: space traveled;
t: Time interval.
2) Clockwise Position Function for Uniform Movement
The position hour function determines the position occupied by a rover from its speed and elapsed time. It is necessary to know the graphics that involve this function.
S: final position occupied by the mobile;
s0: initial position occupied by the mobile;
v: mobile speed;
t: instant of time considered.
3) Torricelli Equation
Torricelli's equation is extremely important as it does not depend on time.
v: ultimate speed;
v0: initial speed;
The: mobile acceleration;
Δs: space traveled.
4) Wave propagation speed
Waves propagate through space and have their speeds determined from their characteristic frequencies and wavelengths.
v: wave velocity;
λ: wavelength;
f: wave frequency.
5) 1st law of Ohm
Ohm's first law shows that the potential difference (ddp) between two points is the result of the product between the electrical resistance found and the electrical current.
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U: potential difference (ddp);
R: electrical resistance;
i: electric current.
6) Electric power
Power talks about the amount of energy “used” per unit of time. Electric power is given by the product between ddp and electric current.
P: electric power;
U: potential difference (DDP)
i: electric current.
7) Transformation between thermometric scales
There are three scales in official use for determining temperatures: Celsius (°C), Fahrenheit (°F) and Kelvin (K). The equation below allows for the conversion of values between these scales.
TÇ: temperature in Celsius (°C);
TF: temperature in Fahrenheit (ºF);
TK: temperature in Kelvin (K).
8) sensible heat
Sensitive heat is the amount of thermal energy that is supplied to a body without a change in physical state.
Q: amount of heat;
m: substance mass;
ç: specific heat of the substance.
ΔT: temperature variation.
9) linear dilation
When a material is exposed to temperature fluctuations, it swells because of the heat it receives or contracts because of heat loss. Thus, it is possible to measure the increase or decrease of the material.
L: increase suffered by the material;
L0: initial material size;
α: linear expansion coefficient
ΔT: temperature variation.
10) Snell's Law
Snell's law is related to the phenomenon of refraction, when light changes its material medium. This equation shows that the product of the refractive index of the media and the angles of incidence or refraction will always be equal.
N1 and no2: refraction indices;
yes α1: sine of the angle of incidence;
sin α2: sene of the angle of refraction.
By Joab Silas
Graduated in Physics
Would you like to reference this text in a school or academic work? Look:
JUNIOR, Joab Silas da Silva. "10 Essential Physics Equations for Enem"; Brazil School. Available in: https://brasilescola.uol.com.br/fisica/10-equacoes-fisica-essenciais-para-enem.htm. Accessed on June 27, 2021.
