An arrow, starting from rest, leaves the bow with a speed of25
m/s. If the average force exerted on the arrow by the bowwere
tripled, all else remaining the same, with what speed wouldthe
arrow leave the bow?

Respuesta :

Answer:

  • The speed will be [tex]v_f= 43.30 \frac{m}{s}[/tex]

Explanation:

We can use the following kinematics equation

[tex]v_f^2-v_i^2=2 \ a \ d[/tex]

where [tex]v_f[/tex] is the final speed, [tex]v_i[/tex] its the initial speed, a is the acceleration, and d the distance.

The force will be tripled, the force is:

[tex]\vec{F} = m \vec{a}[/tex]

in 1D

[tex]F = m a[/tex]

Now, for the original problem, we have

[tex](25 \frac{m}{s})^2-(0 \frac{m}{s})^2=2 \ a' \ d'[/tex]

[tex](25 \frac{m}{s}))^2=2 \ a' \ d'[/tex]

[tex]625 \frac{m^2}{s^2}=2 \ a' \ d'[/tex]

For the second problem, we have

[tex](v_f})^2-(v_i)^2=2 \ a'' \ d''[/tex]

starting from the rest, we have the same initial velocity.

[tex](v_f})^2-(0\frac{m}{s})^2=2 \ a'' \ d''[/tex]

[tex](v_f})^2=2 \ a'' \ d''[/tex]

As the force is tripled, we have:

[tex]F'' = 3 F'[/tex]

[tex]m'' \ a'' = 3 m' \ a'[/tex]

But the mass its the same,  so

[tex]m' \ a'' = 3 m' \ a'[/tex]

[tex]  a'' = 3 \ a'[/tex]

So the acceleration its also tripled.

[tex](v_f})^2=2 \ (3 * a') \ d''[/tex]

[tex](v_f})^2=3 ( 2 \ ( a' \ d'' )[/tex]

As the distance traveled by the arrow must also be the same, we have:

[tex](v_f})^2=3 ( 2 \ ( a' \ d' )[/tex]

[tex](v_f})^2=3 (625 \frac{m^2}{s^2})[/tex]

[tex]v_f= \ sqrt{3 (625 \frac{m^2}{s^2})}[/tex]

[tex]v_f= \ sqrt{3} 25 \frac{m}{s}[/tex]

[tex]v_f= 43.30 \frac{m}{s}[/tex]

And this will be the speed from the arrow leaving the bow.