A 80 kg cannonball is fired from a 500 kg cannon with an acceleration of 80 m / s2. The magnitude of the recoil acceleration of the cannon is m / s?. QUESTION 16 A ball hangs at rest from a string attached to the ceiling. The string pulls up on the ball with a force equal to its weight. The 30 law pair to the downward force of the earth on the ball is a(n)... O upward force exerted by the ball on the string O downward force exerted by the ball on the string O upward force exerted by the ball on the earth O upward force exerted by the string on the earth O downward force exerted by the earth on the ball O downward force exerted by the earth on the string