Question concerning initial velocity

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SUMMARY

The discussion centers on calculating the initial velocity required for an athlete to achieve a long jump of 7.78 meters at a take-off angle of 31.6°. The correct formula to use is Distance = V02sin(2θ)/g, where V0 is the initial velocity, θ is the angle of take-off, and g is the acceleration due to gravity. The participant initially derived an incorrect formula, indicating a misunderstanding of the algebra involved. The discussion emphasizes the importance of correctly applying the physics of projectile motion to solve such problems.

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  • Understanding of projectile motion principles
  • Familiarity with trigonometric functions, specifically sine and cosine
  • Basic algebra skills for manipulating equations
  • Knowledge of gravitational acceleration (g = 9.81 m/s2)
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  • Study the derivation of the projectile motion equations
  • Learn how to apply the range formula for projectile motion
  • Practice solving problems involving initial velocity and angles in projectile motion
  • Explore the effects of air resistance on projectile motion
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Students studying physics, particularly those focusing on mechanics and projectile motion, as well as educators looking for examples of common mistakes in algebraic problem-solving.

Casimi
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Homework Statement



An athlete executing a long jump leaves the ground at a 31.6° angle and travels 7.78 m. What was the take-off speed?

I have tried to solve this question but somehow keep arriving at the wrong answer. The formula that I derived is :

distance=V(initial)*sin^2(theta)/g

Where am I going wrong here? Any help would be appreciated.
 
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Are you computing

distance=V0sin2θ/g

OR

Distance = V02sin2θ/g?

The second one is the one should use.
 
It seems as if I derived the wrong formula via a mistake in my algebra.

Thank you so much!
 
i get a different formula for it.

First take the vertical component, and find the total time taken. Now take the horizontal component of the velocity and multiply by time to find the expression for distance(range)

Substitute and get your answerEDIT: rock.freak answered first, i guess...
 
It seems like I should take more time to organize my thoughts and perform my algebra correctly. Simple mistakes are always my downfall!
 

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