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During a fireworks display, a shell is shot into the air with an initial speed of [tex]70.0 \, \text{m/s}[/tex] at an angle of [tex]75.0^\circ[/tex] above the horizontal, as shown below. The fuse is timed to ignite the shell just as it reaches its highest point above the ground.

a. Calculate the height at which the shell explodes.
b. How much time passed between the launch of the shell and the explosion?
c. What is the horizontal displacement of the shell when it explodes?

Answer :

The shell explodes at a height of approximately 241.188 m, after about 6.890 s from launch, with a horizontal displacement of around 120.896 m.

To solve this problem, we can use kinematic equations for projectile motion. We'll break it down into parts:

Given:

- Initial velocity [tex](\( v_0 \))[/tex] = 70.0 m/s

- Launch angle [tex](\( \theta \))[/tex]= 75.0°

- Acceleration due to gravity [tex](\( g \)) = \( 9.81 \, \text{m/s}^2 \)[/tex]

a.Calculate the height at which the shell explodes:

To find the maximum height [tex](\( h_{\text{max}} \))[/tex] reached by the shell, we'll use the kinematic equation:

[tex]\[ h_{\text{max}} = \frac{{v_0^2 \sin^2 \theta}}{{2g}} \][/tex]

Substitute the given values:

[tex]\[ h_{\text{max}} = \frac{{(70.0 \, \text{m/s})^2 \times (\sin 75.0°)^2}}{{2 \times 9.81 \, \text{m/s}^2}} \][/tex]

[tex]\[ h_{\text{max}} \approx \frac{{4900 \times 0.965925826)}}{{19.62}} \][/tex]

[tex]\[ h_{\text{max}} \approx \frac{{4733.64015}}{{19.62}} \][/tex]

[tex]\[ h_{\text{max}} \approx 241.188 \, \text{m} \][/tex]

So, the height at which the shell explodes is approximately [tex]\( 241.188 \, \text{m} \).[/tex]

b.Calculate the time passed between the launch and the explosion:

The time taken to reach the maximum height [tex](\( t_{\text{max}} \))[/tex] can be calculated using the equation:

[tex]\[ t_{\text{max}} = \frac{{v_0 \sin \theta}}{{g}} \][/tex]

Substitute the given values:

[tex]\[ t_{\text{max}} = \frac{{70.0 \times \sin 75.0°}}{{9.81}} \][/tex]

[tex]\[ t_{\text{max}} \approx \frac{{70.0 \times 0.965925826}}{{9.81}} \][/tex]

[tex]\[ t_{\text{max}} \approx \frac{{67.61590782}}{{9.81}} \][/tex]

[tex]\[ t_{\text{max}} \approx 6.890 \, \text{s} \][/tex]

c.Calculate the horizontal displacement of the shell when it explodes:

The horizontal displacement d can be calculated using the equation:

[tex]\[ d = v_0 \cos \theta \times t_{\text{max}} \][/tex]

Substitute the given values:

[tex]\[ d = 70.0 \times \cos 75.0° \times 6.890 \][/tex]

[tex]\[ d \approx 70.0 \times 0.258819045 \times 6.890 \][/tex]

[tex]\[ d \approx 120.896 \, \text{m} \][/tex]

So, the horizontal displacement of the shell when it explodes is approximately [tex]\( 120.896 \, \text{m} \).[/tex]

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Rewritten by : Brahmana