The recoil velocity of the rifle is 11.25 m/s in the opposite direction of the bullet.
To find the recoil velocity of the rifle, we can use the principle of conservation of momentum. The momentum of the bullet before firing is given by its mass (0.06 kg) multiplied by its velocity (600 m/s), which equals 36 kg m/s. According to the principle of conservation of momentum, the total momentum before firing must be equal to the total momentum after firing.
Since the rifle is initially at rest, its momentum before firing is zero. Therefore, the total momentum after firing must also be zero. The recoil velocity of the rifle can be calculated by dividing the momentum of the bullet (36 kg m/s) by the mass of the rifle (3.2 kg), which gives a recoil velocity of 11.25 m/s.
The correct answer is B. 6 m/s in the opposite direction of the bullet.