Question

A stone is dropped from a height of 45 m. What is the time taken for the stone to reach the ground?

• A. 3 s
• B. 5 s
• C. 6 s
• D. 9 s

Hint:

Remember: For free fall problems, use the equation \( h = \frac{1}{2} g t^2 \) to find the time taken.

Answer 1

The Correct Option is A

The problem involves calculating the time taken for an object to fall from a certain height under gravity. Here, we use the equation of motion for free fall without initial velocity:
h = ¹⁄₂ gt²

Where:

• h = height (45 m)
• g = acceleration due to gravity (9.8 m/s²)
• t = time in seconds

Substitute the values into the equation:
45 m = ¹⁄₂ (9.8 m/s²) t²
Solving for t²:
45 m = 4.9t²
t² = ^{45 m}⁄_{4.9 m/s²}
t² = 9.18
t ≈ √9.18 ≈ 3.03 s

Rounding to the nearest second, t ≈ 3 s.

Therefore, the time taken for the stone to reach the ground is approximately 3 seconds, confirming the correct answer is 3 s.