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Find the average force exerted by the bat on the ball if the two are in contact for...

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jayjay00 | Student, Undergraduate | (Level 1) Honors

Posted October 27, 2009 at 9:50 PM via web

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Find the average force exerted by the bat on the ball if the two are in contact for 0.0028 s. Answer in units of N.

A pitcher throws a 0.15kg baseball so that it crosses home plate horizontally with a speed of 14m/s. It is hit straight back at the pitcher with a final speed of 32m/s.

Given: Choose the positive direction to be from the pitcher to the plate (some answers may be negative).

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krishna-agrawala | College Teacher | (Level 3) Valedictorian

Posted October 27, 2009 at 10:24 PM (Answer #1)

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Given:

Initial velocity = u = 14 m/s

Final velocity = v = -32 m/s

Time taken for change in velocity = t = 0.0028 s

Mass of ball = m = 0.15 kg

We know:

Force exerted = acceleration*mass = a*m, and

Acceleration = a = (v - u)/t

Substituting given value of u,v and t we get

a = (-32 - 14)*0.0028 = -46*0.0028 = 0.1288 m/s^2

Substituting this value of acceleration in equation for force

Force exerted = 0.1288*0.15 = 0.01932 N

Answer: Average force exerted by the bat on ball is 0.01932 N

 

 

 

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neela | High School Teacher | (Level 3) Valedictorian

Posted October 27, 2009 at 10:25 PM (Answer #2)

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The mass of the ball the pitcher throws is 0.15 kg. The velocity of the baseball is 14m/s. The velocity of the ball after hit = -32m/s after hit(negative as,the direction of the velocity is opposite and towards the pitcher).

Therefore , the change of momentum = mass of the ball*(finalal velocity)-mass of the ball*(initial velocity of the ball after hit))= 0.15kg(-32m/s)-0.15kg(14m/s) = -6.9kg m/s. As the change of momentum took in 0.0028 seconds, the force on the ball is the rate of change in the momentum =[-6.9kg m/s]/(0.0028s) = -2464.2857 N, the negative indicates the direction is from plate towards the pitcher.

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