contestada

An instrument is thrown upward with a speed of 15 m/s on the surface of planet X where the acceleration due to gravity is 2.5 m/s2 and there is no atmosphere. How long does it take for the instrument to return to where it was thrown?

Respuesta :

Answer: 12 s

Explanation:

The situation described here is parabolic movement. However, as we are told the instrument is thrown upward from the surface, we will only use the equations related to the Y axis.

In this sense, the main movement equation in the Y axis is:

[tex]y-y_{o}=V_{o}.t-\frac{1}{2}g.t^{2}[/tex]    (1)

Where:

[tex]y[/tex]  is the instrument's final position  

[tex]y_{o}=0[/tex]  is the instrument's initial position

[tex]V_{o}=15m/s[/tex] is the instrument's initial velocity

[tex]t[/tex] is the time the parabolic movement lasts

[tex]g=2.5\frac{m}{s^{2}}[/tex]  is the acceleration due to gravity at the surface of planet X.

As we know [tex]y_{o}=0[/tex]  and [tex]y=0[/tex] when the object hits the ground, equation (1) is rewritten as:

[tex]0=V_{o}.t-\frac{1}{2}g.t^{2}[/tex]    (2)

Finding [tex]t[/tex]:

[tex]0=t(V_{o}-\frac{1}{2}g.t^{2})[/tex]   (3)

[tex]t=\frac{2V_{o}}{g}[/tex]   (4)

[tex]t=\frac{2(15m/s)}{2.5\frac{m}{s^{2}}}[/tex]   (5)

Finally:

[tex]t=12s[/tex]