Physics Speed Equation

Question

A toy gun fires at 5.93 g projectile disc by using a compressed spring (K=2.18×10^3 N/M) and 19.1 cm long barrel. As the disc travels through the barrel, it experience a constant frictional force of 0.82 N. If the Spring is compressed 16.4 mm what is the speed of the disc as it leaves the gun?

Answer 1

-(1/2)*K*(X2^2-X1^2) - fk * L = (1/2) * M * (V2^2-V1^2)

K = 2.18×10^3 N/M

L = 0.191 m

fk = 0.82N

X2 = 0

X1 = 0.0164m

M = 5.93 g / 1000 = 0.00593 kg

-(1/2)*K*(X2^2-X1^2) - fk * L = (1/2) * M * (V2^2-V1^2)

Set X2 = 0, V1 = 0

-(1/2)*K*(-X1^2) - fk * L = (1/2) * M * (V2^2)

V2^2 = (2/M)[(1/2)*K*(X1^2)-fk * L]

V2 = 6.786 m/s