Average force exerted by the ball

[mathcrzy]

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

 

[PhanthomJay]

you have calculated the kinetic energy lost. The problem asks for the force. What equation(s) might you use to solve for F?

 

[mathcrzy]

F=(1/2)kx^2

 

[chocokat]

Be careful with your calculations - baseball m = 145 g ...

 

[PhanthomJay]

F=(1/2)kx^2

No, you're fishing in the wrong pool! Are you familiar with energy methods, or kinematics and Newton 2?

 

[mathcrzy]

would the equation just be F=mv?

 

[PhanthomJay]

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.

 

[mathcrzy]

Vf^2=Vi^2*a*d

 

[mathcrzy]

0=1225+2*a*.15
-2*a*.15=1225
a*.15=-612
a=-4083.3

 

[PhanthomJay]

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.