Projectile Motion in Combination with Energy Problem

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SUMMARY

The discussion centers on calculating the required extension of a spring in a toy rifle to hit a target 15 meters away when fired at a 45-degree angle. The spring has a mass of 0.008 kg and a spring constant of 350 N/m. The key equations used include the potential energy of the spring (E = 1/2(k)(x)2), kinetic energy (KE = 1/2(m)(v)2), and the horizontal range formula for projectile motion. The solution involves equating the potential energy of the spring to the kinetic energy needed to achieve the target distance.

PREREQUISITES
  • Understanding of spring mechanics, specifically Hooke's Law (F = kx).
  • Familiarity with energy conservation principles, particularly potential and kinetic energy equations.
  • Knowledge of projectile motion equations, including range calculations.
  • Basic algebra skills for solving equations.
NEXT STEPS
  • Study the derivation of the horizontal range formula for projectile motion.
  • Explore the relationship between spring compression and energy storage in springs.
  • Learn how to apply conservation of energy principles in mechanical systems.
  • Investigate the effects of angle on projectile motion and how it influences range.
USEFUL FOR

Students studying physics, particularly those focusing on mechanics and energy conservation, as well as educators looking for practical examples of applying theoretical concepts in projectile motion and spring dynamics.

Bound
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Homework Statement


A toy rifle shoots a spring of mass 0.008kg and with a spring constant of 350 N/m. You wish to hit a target horizontally a distance of 15m away by pointing the rifle 45o above the horizontal. How far should you extend the spring in order to reach the target?


Homework Equations


E = 1/2(k)(x)2
F = kx
KE = 1/2(m)(v)2
Any relevant kinematics formulae.


The Attempt at a Solution


Normally for questions like this I would equate potential spring energy to the kinetic energy, but here I am missing a velocity as well as the spring compression length so I am a little lost.
 
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Bound said:

Homework Statement


A toy rifle shoots a spring of mass 0.008kg and with a spring constant of 350 N/m. You wish to hit a target horizontally a distance of 15m away by pointing the rifle 45o above the horizontal. How far should you extend the spring in order to reach the target?


Homework Equations


E = 1/2(k)(x)2
F = kx
KE = 1/2(m)(v)2
Any relevant kinematics formulae.


The Attempt at a Solution


Normally for questions like this I would equate potential spring energy to the kinetic energy, but here I am missing a velocity as well as the spring compression length so I am a little lost.
Use the formula for horizontal range for projectile motion letting sin2θ = 1 and R = 15 m. to determine the initial velocity v that is needed. From that you can work out the kinetic energy and, therefore, the potential energy of the spring.

AM
 

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