Projectile Kinetic Energy and Recoil in Spring Gun Experiment

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SUMMARY

The discussion focuses on the physics of a projectile fired from a spring gun on a frictionless surface, emphasizing the conservation of momentum and kinetic energy. The kinetic energy of the projectile is denoted as K, while the combined mass of the gun and projectile is M2. The recoil kinetic energy of the gun is derived from the equation (M1/(M2-M1))K, where M1 is the mass of the projectile. The initial momentum is confirmed to be zero, leading to the conclusion that the final velocities of both the projectile and the gun must be calculated using vector subtraction.

PREREQUISITES
  • Understanding of kinetic energy formulas, specifically K = 0.5 * m * v^2
  • Knowledge of momentum conservation principles in physics
  • Familiarity with vector quantities and their operations
  • Basic grasp of mass and its relation to motion in a system
NEXT STEPS
  • Study the derivation of the conservation of momentum in two-body systems
  • Explore advanced applications of kinetic energy in different physical scenarios
  • Learn about the implications of frictionless surfaces on motion dynamics
  • Investigate the effects of varying mass ratios on recoil and projectile motion
USEFUL FOR

Students studying physics, particularly those focusing on mechanics, as well as educators and anyone interested in understanding the principles of projectile motion and recoil dynamics.

CoreanJesus

Homework Statement


A projectile of mass M1 is fired horizontally from a spring gun that is initially at rest on a frictionless surface. The combined mass of the gun and projectile is M2. If the kinetic energy of the projectile after firing is K, the gun will recoil with a kinetic energy equal to...

Homework Equations


this is part of the problem.
I know you need the kinetic energy formula but I don't get the other formula.

The Attempt at a Solution


N/A Answer is (M1/(M2-M1))K
 
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Hi,

You will need to take into consideration that the total momentum is conserved.
 
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But what should the initial momentum be? 0?
 
Yes, the initial momentum is zero. That does not mean that the final velocity of the gun and of the projectile will be also zero. Do not forget that velocity (and momentum too) is a vector. So if you have two velocities (or momentum) in the opposite directions, you need to subtract one velocity from the other.
 
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so M1V1=(M2-M1)V2
K=.5M1V1^2
KE=.5(M2-m1)V2^2 and plugin?
 
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Exactly.
 
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Thank you so much!
 

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