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Average force exerted by the ball

  • Thread starter mathcrzy
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  • #1
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Homework Statement



A baseball (m = 145 g) traveling 35 m/s moves a fielder's glove backward 15 cm when the ball is caught. What was the average force exerted by the ball on the glove?
Magnitude

Homework Equations



-(1/2)mv^2

The Attempt at a Solution



(1/2)(145)(35)^2=-88812.5
 

Answers and Replies

  • #2
PhanthomJay
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you have calculated the kinetic energy lost. The problem asks for the force. What equation(s) might you use to solve for F?
 
  • #3
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F=(1/2)kx^2
 
  • #4
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Be careful with your calculations - baseball m = 145 g ...
 
  • #5
PhanthomJay
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F=(1/2)kx^2
No, you're fishing in the wrong pool! Are you familiar with energy methods, or kinematics and Newton 2?
 
  • #6
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would the equation just be F=mv?
 
  • #7
PhanthomJay
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would the equation just be F=mv?
You mean F=ma, don't you? So how would you calculate 'a' knowing that the ball goes from 35m/s to a stop in a 15cm distance? (Hint: use the kinematic equation that relates distance with acceleration and velocity change, and watch your units.
 
  • #8
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Vf^2=Vi^2*a*d
 
  • #9
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0=1225+2*a*.15
-2*a*.15=1225
a*.15=-612
a=-4083.3
 
  • #10
PhanthomJay
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0=1225+2*a*.15
-2*a*.15=1225
a*.15=-612
a=-4083.3
Yes that looks good, don't forget units of a is m/sec^2. What does the minus sign tell you? Now plug it into F=ma to solve for F, watch units, and interpert the significance of the minus sign.
 

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