The speed of a box traveling on a horizontal friction surface changes from vi = 13 m/s to vf = 11.5 m/s in a distance of d = 8.5 m. "How long in seconds did it take for the box to slow by this amount, assuming the acceleration is constant?"

Respuesta :

Answer:

0.68 s

Explanation:

We are given that

Initial velocity of box=[tex]u=13m/s[/tex]

Final velocity of box=v=11.5 m/s

Distance=d=8.5 m

We have to find the time taken by box to slow by this amount.

We know that

[tex]v^2-u^2=2as[/tex]

Substitute the values

[tex](11.5)^2-(13)^2=2a(8.5)[/tex]

[tex]132.25-169=17a[/tex]

[tex]-36.75=17a[/tex]

[tex]a=\frac{-36.75}{17}=-2.2m/s^2[/tex]

We know that

Acceleration=[tex]a=\frac{v-u}{t}[/tex]

Substitute the values

[tex]-2.2=\frac{11.5-13}{t}[/tex]

[tex]-2.2=\frac{-1.5}{t}[/tex]

[tex]t=\frac{1.5}{2.2}=0.68 s[/tex]

Hence, the time taken by box to slow by this amount=0.68 s

"0.68 s" would be taken by the box to slow by this amount.

Given values are:

Initial velocity,

  • u = 13 m/s

Final velocity,

  • v = 11.5 m/s

Distance,

  • d = 8.5 m

As we know,

→            [tex]v^2-u^2 = 2as[/tex]

By substituting the values, we get

→ [tex](11.5)^2-(13)^2 = 2a(8.5)[/tex]

→     [tex]132.25-169=17 a[/tex]

→                       [tex]a = -\frac{36.75}{17}[/tex]

                           [tex]= -2.2 \ m/s^2[/tex]

hence,

Acceleration, [tex]a = \frac{v-u}{t}[/tex]

                     [tex]-2.2 = \frac{11.5-13}{t}[/tex]

                           [tex]t = \frac{1.5}{2.2}[/tex]

                              [tex]= 0.68 \ s[/tex]

Thus the above response is right.

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