Question

A bullet makes n turns inside the barrel of length of a rifle and emerges from it with a speed v. Assuming that the bullet moves inside the barrel with a uniform acceleration, the angular velocity of the bullet about its longitudinal axis as it emerges from the barrel is

• A. $\frac{v}{\mathcal{l}}$
• B. $\frac{2\pi nv}{\mathcal{l}}$
• C. $\frac{\pi n}{2v}$
• D. None of these

Answer 1

Answer: (B)

$\frac{2\pi nv}{\mathcal{l}}$

Answer 2

v = at , ω = αt

2πn = $\frac{1}{2}$αt²

= $\frac{1}{2}$at² ⇒$\frac{2\pi n}{\mathcal{l}} = \frac{\alpha}{a}$ = $\frac{\omega}{v}$

ω = $\frac{2\pi n}{\mathcal{l}}$v , Hence, (2) is correct.