Projectile Motion: Finding Distance to Clear a Wall

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SUMMARY

The discussion centers on calculating the horizontal distance a ball must travel to clear a 2-meter high wall when thrown at an angle of 60 degrees with an initial velocity of 20 meters per second. The correct height equation is identified as h = (v(subzero) * sin(theta))^2 / (2g), where g is the acceleration due to gravity (9.8 m/s²). The user initially misapplied the equation, resulting in an incorrect height calculation. The correct horizontal distance to clear the wall is determined to be approximately 1.2 meters or 33.5 meters, depending on the interpretation of the problem.

PREREQUISITES
  • Understanding of projectile motion principles
  • Familiarity with trigonometric functions, specifically sine
  • Knowledge of gravitational acceleration (g = 9.8 m/s²)
  • Ability to manipulate algebraic equations
NEXT STEPS
  • Review the derivation of the projectile motion equations
  • Practice solving similar problems involving angles and initial velocities
  • Learn about the range of a projectile and how to calculate it
  • Explore the impact of different launch angles on projectile distance
USEFUL FOR

Students studying physics, educators teaching projectile motion, and anyone interested in mastering the calculations involved in trajectory analysis.

smartblonde
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Homework Statement


A ball is thrown at 60deg with v(subzero) = 20 meters/sec to clear a wall that is 2 meters high. how far away is the wall?


Homework Equations


h=((v(subzero)*sin(theta))^2)/g


The Attempt at a Solution


I tried inserting my givens into the height equation and came up with a very funky answer. here 'tis:
h= ((20sin60)^2)/9.8=30.6
my answer key says x=1.2 or 33.5. I know I'd have to subtract 2 from the number I got, but that doesn't explain the discrepancy between my answer and the one the text gives. what am I doing wrong?
 
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Your "height equation" is slightly wrong. There's a factor of 2 somewhere you forgot to include.
 
oh--it's supposed to be 2g, right? well, that still gives me 15.3 which is not the answer I'm looking for. I've used this same equation (correctly) on other problems and I'm not sure why this one isn't coming out the same.
 

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