A bullet shot straight up returns to its starting point in 10 s. Its initial speed was:
Correct answer: B. 49 ms-1
- A. 9.8 ms-1
- B. 49 ms-1
- C. 24.5 ms-1
- D. 98 ms-1
Explanation
To solve this problem, we first note that the total time for the bullet to return to its starting point is 10 seconds. This means it takes 5 seconds to reach the highest point of its trajectory.Using the equation for uniformly accelerated motion, vf = vi + at, and considering that at the highest point the final velocity vf is 0, we can rearrange the equation to find the initial velocity vi: vi = gt.Here, g is the acceleration due to gravity, approximately 9.8 ms-2, and t is 5 seconds (time to reach the highest point). Therefore, vi = 9.8 ms-2 x 5 s = 49 ms-1.The other options are incorrect: 9.8 ms-1 is the value of g, not the initial speed; 24.5 ms-1 is half of the correct answer, indicating confusion with time; and 98 ms-1 is double the correct initial speed, likely due to miscalculation.
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