Confirm Your Solving a Physics Problem

[Matt1234]

hello,

Homework Statement

[PLAIN]http://img526.imageshack.us/img526/6656/69304345.jpg

Homework Equations

m *v1 + integral Force dt = m v2

Ive tried several methods for this problem but keep comming up with 489.8 ft/s. Can someone confirm?

 

[PhanthomJay]

Your equation is correct, but your answer is not. I suspect you mixed up your plus/minus signs and put in the wrong value for the mass. If you could show your work, I can see where your error might be.

 

[Matt1234]

Hi there:

Here was my attempt.

[PLAIN]http://img256.imageshack.us/img256/1238/lastscannk.jpg

i think I am not applying the integral properly

 

[PhanthomJay]

Your integral is fine...the error is all in the plus and minus sign. Since force and velocity are vectors, they have direction. The initial velocity is in what direction? The final velocity is in what direction? The net force is in what direction? Correct your signage and you'll be all set.

 

[Matt1234]

Your integral is fine...the error is all in the plus and minus sign. Since force and velocity are vectors, they have direction. The initial velocity is in what direction? The final velocity is in what direction? The net force is in what direction? Correct your signage and you'll be all set.

ok I am pretty sure the correct answer is 90 ft/s. Can you please confirm. My reasoning is that the initial quantity is negative and the impulse is positive and the final velocity is positive. (+ y direction) this was the convention i used.

Can you confirm?

Thank you for your assistance, i appreciate your help.

 

[PhanthomJay]

ok I am pretty sure the correct answer is 90 ft/s. Can you please confirm. My reasoning is that the initial quantity is negative and the impulse is positive and the final velocity is positive. (+ y direction) this was the convention i used.

Can you confirm?

Thank you for your assistance, i appreciate your help.

Yes, excellent, good work.

 

[Matt1234]

great, thank you sir!