A stone is thrown horizontally from a height of 20 meters. How long does it take

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Question: A stone is thrown horizontally from a height of 20 meters. How long does it take to hit the ground? (Assume g = 9.8 m/s²)

Options:

Correct Answer: 2 s

Solution:

Using the formula t = √(2h/g), where h = 20 m and g = 9.8 m/s², we get t = √(2 * 20 / 9.8) ≈ 2.02 s.

A stone is thrown horizontally from a height of 20 meters. How long does it take to hit the ground? (Assume g = 9.8 m/s²)

A stone is thrown horizontally from a height of 20 meters. How long does it take to hit the ground? (Assume g = 9.8 m/s²)

Step 1: Identify the height from which the stone is thrown. In this case, the height (h) is 20 meters.
Step 2: Identify the acceleration due to gravity (g). Here, g is given as 9.8 m/s².
Step 3: Use the formula to calculate the time (t) it takes for the stone to hit the ground. The formula is t = √(2h/g).
Step 4: Substitute the values into the formula: t = √(2 * 20 / 9.8).
Step 5: Calculate the value inside the square root: 2 * 20 = 40, then divide by 9.8, which gives approximately 4.08.
Step 6: Take the square root of 4.08 to find t. The square root of 4.08 is approximately 2.02 seconds.
Step 7: Conclude that it takes about 2.02 seconds for the stone to hit the ground.

Projectile Motion – The question tests understanding of the time of flight for an object in free fall, independent of horizontal motion.
Kinematic Equations – Application of the kinematic equation for vertical motion to determine the time taken to fall a certain height.