Answer:
r₂ = 1.5 ft
t = 0.75 s
Explanation:
W = 4 lb ⇒ m = W/g = 4 lb / 32.2 ft/s² = 0.12 slug
v₁ = 6 ft/s
r₁ = 3 ft
v₂ = 12 ft/s
r₂ = ?
t = ?
vr = 2 ft/s
Conserving angular momentum we have:
m*v₁*r₁ = m*v₂*r₂ ⇒ r₂ = v₁*r₁ / v₂
⇒ r₂ = (6 ft/s*3 ft) / (12 ft/s) = 1.5 ft
Now, we get the time as follows:
vr = d / t ⇒ t = d / vr
where d is
d = Δr = r₁ - r₂ = 3 ft - 1.5 ft = 1.5 ft
finally
t = 1.5 ft / 2 ft/s
⇒ t = 0.75 s
