How Is Impulse Calculated in Baseball Physics?

[GiantSheeps]

Homework Statement

A(n) 0.142 kg baseball is thrown with a speed
of 19.5 m/s. It is hit straight back at the
pitcher with a final speed of 26.6 m/s.
What is the magnitude of the impulse delivered
to the ball?
Answer in units of kg · m/s

(part 2) Find the average force exerted by the bat on
the ball if the two are in contact for 0.00109 s.
Answer in units of N

Homework Equations

F*t=mvf-mvi

The Attempt at a Solution

m= 0.142 and vf = 26.6, so mvf = 3.772, vi = 19.5 so mvi = 2.769
3.772 - 2.769 = 1.0082
which was wrong of course...
i think i need to do something with the t in the equation, but there is no t given in the problem

i also tried it with vi = 0, since velocity would be zero while the ball s on the bat, but that answer (3.772) was wrong as well

 

[Doc Al]

m= 0.142 and vf = 26.6, so mvf = 3.772, vi = 19.5 so mvi = 2.769
3.772 - 2.769 = 1.0082
which was wrong of course...
i think i need to do something with the t in the equation, but there is no t given in the problem

You forgot to take the direction (and thus the sign) of the velocities into account.

 

[Jazz]

Hi,

Is the ball hit in the same direction it is first thrown?

 

[GiantSheeps]

oh okay i see, so instead of 3.772 - 2.769, it would be 3.772 + 2.769 = 6.541?

 

[GiantSheeps]

it is! thank you so much! for the second part of the question, I would divide the impulse by the time? 6.541/.00109 = 6000.917431 ... that seems a bit large though...

 

[GiantSheeps]

oh wait nevermind, this is a baseball being hit off of a bat, those things come off HARD. haha if anything that 6000 number seems a bit on the small side... it is the correct answer though so thank you thank you so much