- #1

Dorothy Weglend

- 247

- 2

The ball moves 15.0 cm through the barrel, with friction force of 0.0320 N between thebarrel and the ball. With what speed does the projectile leave the barrel of the cannon?

I thought this problem was simple, but the answer 'in the back' is different from what I am getting, so I thought I would ask for some help.

I use

mv^2/2 = kx^2/2 - fk(x+d)

x = compression of spring, d = distance along the barrel, so

m = 5.32 * 10^-3 m,

k = 8 N/m

x = 0.05 m

k = 8 N/m

fk = 0.032 N

d = 0.15 m

With these figures, I get v = 1.17 m/s.

The answer in the back is 1.40 m/s.

Can anyone see where I am going wrong?

Dorothy