How Fast Does a Ball Shoot from a Toy Cannon with Friction?

[closer]

A toy cannon uses a spring to project a 5.30 g soft rubber ball. The spring is originally compressed by 5.00 cm and has a force constant of 9.00 N/m. When it is fired, the ball moves 16.0 cm through the horizontal barrel of the cannon, and a constant frictional force of 0.0320 N exists between barrel and ball.

(a) With what speed does the projectile leave the barrel of the cannon?

W_net = $$\Delta$$KE
W_s - W_fk = .5mv² - 0
.5kx² - f_kd = .5mv²
.5(9)(.05²) - (.032)(.11) = .5(.0053)v²
v = 1.7079

Final answer is incorrect. Any ideas?

 

[krausr79]

Have you tried replacing .11 with .16? Friction acts over full length of barrel. What is the answer?