A cannon ball (mass = 2 kg) is fired at a target of 500 meters away. The 400 kg cannon recoils by 50 cm. Assuming cannon ball moves with constant velocity, when will it hit the target? [Resistance offered by ground to cannon is 100 N]

Force by ground on the cannon = 100N.

Work done by ground on the cannon = 100 x(0.5) = 50J.

Applying conservation of energy

work done by ground on canon = Kinetic energy of canon immediately after firing = (1/2) mv2= 50J.

Velocity of cannon (v) = 0.5m/sec.

By applying law of conservation of momentum

400(0.5) = 2 (velocity of cannon ball)

Velocity of canon ball = 100m/sec.

Time taken by the canon ball to hit = 500/100 = 5 seconds.

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