Calculating Cannon Ball Barrel Length: Impulse and Velocity

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SUMMARY

The discussion focuses on calculating the barrel length of a cannon based on impulse and velocity. The impulse is given as 2.5 x 103 N·s, and the mass of the cannon ball is 65 kg. The cannon ball exits the cannon at a velocity of 120 km/h, which is equivalent to 33.33 m/s. The user initially calculated the barrel length as 3.85 m but found it incorrect. The correct approach involves using the impulse-momentum theorem and kinematic equations to determine both the acceleration and the distance traveled within the barrel.

PREREQUISITES
  • Understanding of impulse and momentum concepts
  • Familiarity with kinematic equations
  • Basic knowledge of Newton's second law (F=ma)
  • Conversion of units (e.g., km/h to m/s)
NEXT STEPS
  • Review the impulse-momentum theorem and its applications
  • Study kinematic equations in detail, focusing on distance and acceleration
  • Practice unit conversions, specifically between km/h and m/s
  • Explore examples of similar physics problems involving projectile motion
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Students studying physics, particularly those focusing on mechanics and dynamics, as well as educators looking for practical examples of impulse and motion calculations.

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Homework Statement



The impulse on a human cannon ball is 2.5  103 N·s. The cannon
ball has a mass of 65 kg.

Homework Equations



How long is the barrel of the cannon if the cannon ball leaves the
cannon at 120 km/h?

The Attempt at a Solution



I used the formula J=ma(delta t)
(2.5x 10^3)=(65)(a)(0.2)

to find the acceleration. Then, I used the formula d=v1(t)+(1/2)(a)(t^2) to find the distance, and I got 3.85 m, but the answer at the back is wrong.

Can anybody help me?
 
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How did you get the time of 0.2 seconds ?
 
That's given in part a of the question, which I already got. Here's the entire question:

The impulse on a human cannon ball is 2.5  103 N·s. The cannon
ball has a mass of 65 kg.
a) What force does the cannon exert on the human cannon ball if
it takes 0.2 s for the human cannon ball to leave the cannon?
b) How long is the barrel of the cannon if the cannon ball leaves the
cannon at 120 km/h?
 

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