brazil-enem

2021 enem__day2

2 maths questions

Q94 Projectiles Clearing an Obstacle or Passing Through a Point View
The figure was extracted from an old computer game, called Bang! Bang!
In the game, two competitors control cannons A and B, firing bullets alternately with the objective of hitting the opponent's cannon; to do this, they assign estimated values for the magnitude of the initial velocity of firing ($\left|\overrightarrow{v_0}\right|$) and for the firing angle ($\theta$).
At a certain moment in a match, competitor B must fire; he knows that the bullet fired previously, $\theta = 53^{\circ}$, passed tangentially through point $\boldsymbol{P}$.
In the game, $|\vec{g}|$ equals $10 \mathrm{~m/s}^2$. Consider $\sin 53^{\circ} = 0.8$, $\cos 53^{\circ} = 0.6$ and negligible action of dissipative forces.
Based on the given distances and maintaining the last firing angle, what should be, approximately, the smallest value of $\left|\overrightarrow{v_0}\right|$ that would allow the shot fired by cannon $\mathbf{B}$ to hit cannon $\mathbf{A}$?
(A) $30 \mathrm{~m/s}$.
(B) $35 \mathrm{~m/s}$.
(C) $40 \mathrm{~m/s}$.
(D) $45 \mathrm{~m/s}$.
(E) $50 \mathrm{~m/s}$.
Q95 Exponential Equations & Modelling Threshold or Tipping-Point Calculation in Applied Exponential Models View
Organochlorine pesticides were widely used in agriculture; however, due to their high toxicity and persistence in the environment, they were banned. Consider the application of 500 g of an organochlorine pesticide to a crop and that, under certain conditions, the half-life of the pesticide in the soil is 5 years.
The mass of pesticide over 35 years will be closest to
(A) $3.9 \mathrm{~g}$.
(B) $31.2 \mathrm{~g}$.
(C) $62.5 \mathrm{~g}$.
(D) $125.0 \mathrm{~g}$.
(E) $250.0 \mathrm{~g}$.