A projectile is launched at 15 degrees and it's landing height is the same as the launch position. If this is true, then at what other angle can the projectile be launch to achieve the same horizontal displacement?

To determine the angle at which the projectile can be launched to achieve the same horizontal displacement, we can use the principle of symmetry in projectile motion. Here's how you can approach solving this problem:

1. Assume that the launch angle that yields the desired horizontal displacement is θ.

2. Since the projectile lands at the same height as the launch position, we can conclude that the time of flight for the projectile is the same for both the initial and final angles.

3. Calculate the time of flight for the initial launch angle of 15 degrees. The time of flight (t) can be determined using the formula t = (2 * V₀ * sin(θ)) / g, where V₀ is the initial velocity and g is the acceleration due to gravity.

4. Use the same formula to calculate the initial velocity (V₀) for the launch angle of 15 degrees. To do this, you need to know the distance travelled horizontally (d) by the projectile. The formula for horizontal displacement is d = (V₀² * sin(2θ)) / g.

5. Once you have calculated the time of flight and initial velocity for the 15-degree angle, use these values to calculate the launch angle (θ') that yields the same horizontal displacement. Rearrange the formula for horizontal displacement to solve for θ': θ' = (1/2) * arcsin((d * g) / (V₀²)). Note that arcsin denotes the inverse sine function.

6. Substitute the values you obtained for d, g, and V₀ into the formula for θ'. This will give you the angle at which the projectile needs to be launched to achieve the same horizontal displacement as the original 15-degree angle.

By following these steps, you should be able to calculate the launch angle that results in the same horizontal displacement as the initial 15-degree angle.