# GATE Papers >> Mechanical >> 2015 >> Question No 255

Question No. 255

A bullet spins as the shot is fired from a gun. For this purpose, two helical slots as shown in the figure are cut in the barrel. Projections A and B on the bullet engage in each of the slots.

Helical slots are such that one turn of helix is completed over a distance of 0.5 m. If velocity of bullet when it exits the barrel is 20 m/s, its spinning speed in rad/s is _______.

##### Answer : 251 to 252

Solution of Question No 255 of GATE 2015 Mechanical Paper

Time taken for one rev. (0.5 m) =$\frac{0.5}{20}=0.025\;sec$

so.the spinning speed = $\frac{2\mathrm\pi}{0.025}=251.327\;rad/sec$