What Elevation Angle Clears the Wall and Hits the Target?

AI Thread Summary
To determine the appropriate elevation angle for a projectile to clear a 10 m high wall and hit a target 28.9 m away, initial calculations suggest an angle of 44 to 45 degrees, but the correct angle is closer to 65 degrees. The projectile's initial speed is 20 m/s, and the wall is positioned halfway to the target. Using the equations of motion, the calculations show that while the 44-degree angle allows the projectile to clear the wall, it falls short of reaching the target by nearly 12 meters. Adjusting the angle is necessary to ensure both the wall is cleared and the target is hit. Therefore, further analysis and adjustments to the angle are essential for achieving the desired outcome.
rsmseys
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Homework Statement



A projectile, initial speed v = 20 m/s is supposed to hit a target D = 28.9 m away. However an H = 10 m high wall is placed halfway between the launching point and the target. What is the appropriate elevation angle? (in degrees).

Homework Equations



http://en.wikipedia.org/wiki/Equations_of_motion#Equations_of_uniformly_accelerated_linear_motion

The Attempt at a Solution



I got the answer of around 44 to 45 degrees. The correct answer is said to be closer to 65 degrees. Any help in clarifying which answer is right would be helpful, along with solutions. Thanks.
 
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and how did you reach your answer?

According to PF rules no solns can be given... just help or advice.
 
v = at
20sin(x) = 9.8t
20sin(x) / 9.8 = t
s = 1/2(u +v)t
10 = 1/2 * (20sin(x))*(20sin(x))/9.8

Solving for x, the answer for x (the angle) is 44.427 degrees.
 
Not quite, but you're on the right track.

Work it backwards with your result and you'll see that although you just cleared the wall, you missed the target by nearly 12m.
 
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