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A bullet is fired vertically upward and returns to the firing point after 10 seconds. Which of the following statements are correct? (g = 10 m/s²) (A) The net displacement of the bullet in 10 s is zero. (B) The total distance traveled by the bullet in 10 s is 250 m. (C) The rate of change of velocity with time is constant throughout the motion. (D) The bullet is fired with an initial speed of 50 m/s directed vertically upward.

1. The net displacement of the bullet in 10 s is zero.
2. The total distance traveled by the bullet in 10 s is 250 m.
3. The rate of change of velocity with time is constant throughout the motion of the bullet.
4. The bullet is fired at an initial velocity of 50 m/s directed vertically upwards.

Correct answer: The net displacement of the bullet in 10 s is zero.

Solution

Time up = 5 s. v0 = g*t = 10*5 = 50 m/s (D correct). Net displacement = 0 since bullet returns (A correct). Distance up = (1/2)*g*t² = (1/2)*10*25 = 125 m; total = 2*125 = 250 m (B correct). Throughout the motion, gravity acts constantly so a = -g = -10 m/s² = constant, hence rate of change of velocity is constant (C correct). All four statements are correct.

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