Arrow shot from a bow using spring energy

[whoopie88]

Homework Statement

An archer puts a 0.30 kg arrow to the bowstring. An average force of 192 N is exerted to draw the string back 1.3 m. Assume that air resistance is negligible.
(a) Assuming that all the energy goes into the arrow, with what speed does the arrow leave the bow?

(b) If the arrow is shot straight up, how high does it rise?

Homework Equations

All Energy/Work equations

The Attempt at a Solution

Thanks in advance for help!

 

[rock.freak667]

Those values look correct to me.

 

[whoopie88]

Really? o.o I'm doing a Webassign, and it's telling me that my values are incorrect.
I put in 28.85 m/s for (a) and 42.4 m for (b).

Is there something I'm missing? o.o

 

[rock.freak667]

Really? o.o I'm doing a Webassign, and it's telling me that my values are incorrect.
I put in 28.85 m/s for (a) and 42.4 m for (b).

Is there something I'm missing? o.o

Given the values, it should be correct. Realistically speaking, 1.3 m is quite large for an archer to stretch the string.

 

[venkatg]

Really? o.o I'm doing a Webassign, and it's telling me that my values are incorrect.
I put in 28.85 m/s for (a) and 42.4 m for (b).

Is there something I'm missing? o.o

The "average" force is F, so the energy is F * 1.3

or

F = 192 = K* X /2 not K * X

So the velocity is 28.85 * sqrt(2) = 40.8m/sec