UPDATED!

Another question im having difficult understanding, if someone could help me with what formula to use or the steps involved that would be very helpful, thank you in advance <3


What impulse must be imparted by a baseball bat to a 145 g ball to change its velocity from 40.0 m/s to -50.0 m/s?

#2 If the collision between the baseball and the bat lasts 1.00 ms, what force was exerted on the ball?

For the second part im guessing you just take whats found in question 1 (-13.05Ns) and multiply it by the second of impact, wich in this case is 10^-3(s) or 0.001s?

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Are you talking about how many Newtowns(N) it would take to change the velocity of the baseball?

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You would have to calculate the total force excerted, so it would look a little something like this:


[(0.145kg)x(40m/s)]+[(0.145kg)x(50m/s)]=Force in Newtons(N)

so...

5.8+7.25=N

or...

N=13.05

so 13.05 Newtons

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Vouches:http://sythe.org/showthread.php?t=1115123

Number of members I have gotten banned so far:5

It's a simple change in force to change the velocity. The mass of the ball is constant. The formula would look like this:
P' - P = Impulse (P' is original P)

Old momentum - New Momentum = Impulse
(0.145kg*40m/s) - (.0145kg*-50m/s) = Impulse (in kgm/s or Newtons)

The reason it is added is because the new momentum is negative, so two negatives = a positive. It's incorrect to call it a force as a force is mass x acceleration.


This is of course assuming there is no friction. If there was friction, the newtons needed would be more (increased).

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Impulse is not measured in newtons. Impulse is the integral of the force over the time period at which the force acts( ie it is form of newton-seconds or Ns)

Impulse is what changes an objects momentum, so by applying and impulse your are moving a mass.
So impulse is simply the change in momentum. Careful with the sign

Impulse=mDeltaV
=m(finalV-initialV)
0.145kg*(-50-40)m/s (kgm/s==Ns)

Actually, that answer is correct, and I'm sorry I didn't catch this sooner. The impulse is never in Newtons, it is in N*s (newton seconds), and as the velocity is a vector, the impulse will be negative (as final velocity is negative to the initial). Don't forget your vector arrows! (momentum is also a vector!)

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yea thats right tho lawl

Thank you both very much <3 actually helped, cause my formula sheet doesent give out that.

I have the answer sheet to but that doesent help when i dont know how to get it on a test :P <3

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Formula sheets are absolutely necessary. If you understand calculus and differential equations, every formula you get can be written as the differential of an energy equation from physics 101.

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For #2, what I think they want you to recognize is that F*t = m*v = p, impulse.

You calculated impulse in #1.
So, F*t = -13.05. *t = 0.001s.

(0.001)F = -13.05; F = -13.05/0.001
F = -13050N