Answer:
4. Downward and its value is constant
Explanation:
As this is a case of projectile motion, we use the reference frame where upward direction to be positive for [tex]y[/tex], and in the same way to be negative in the downward direction. On another hand, we have that gravity is always acting this means that gravitational acceleration g is directed downward constantly over the dart not only during the upward but also during the downward part of the trajectory. And it is ruled by the following equations.
For the x-axis
[tex]v_{x}=v_{0}cos(45\°)=constant[/tex]
[tex]x=(v_{0}cos(45\°))t[/tex]
For the y-axis
[tex]v_{y}=v_{0}sin(45\°)-gt[/tex]
[tex]y=v_{0}sin(45\°)t-\frac{1}{2} gt^{2}[/tex]
Where [tex]v_{0}[/tex], is the initial velocity.
