If an object is dropped from rest, what will be its velocity after 15 seconds? (g = 9.8 m/s²)

The correct answer is 147 m/s.

Key Points

• When an object is dropped from rest, its velocity increases uniformly due to the acceleration caused by gravity (g = 9.8 m/s²).
• The formula to calculate the velocity of an object in free fall is v = g × t, where v is the velocity, g is the acceleration due to gravity, and t is the time in seconds.
• Substituting the given values: g = 9.8 m/s² and t = 15 seconds, we get: v = 9.8 × 15 = 147 m/s.
• This calculation assumes that air resistance is negligible, and the object is falling in a vacuum.
• Thus, the velocity of the object after 15 seconds of free fall is 147 m/s, which corresponds to Option 2.

Additional Information

• Free Fall: A condition where an object falls under the sole influence of gravity, with no air resistance acting on it.
• Acceleration Due to Gravity (g): The constant acceleration experienced by an object near the Earth's surface due to the Earth's gravitational pull, approximately equal to 9.8 m/s².
• Uniform Acceleration: In free fall, the acceleration due to gravity remains constant, leading to a uniform increase in velocity over time.
• Time-Velocity Relationship: The velocity of an object in free fall is directly proportional to the time it has been falling, as expressed by the formula v = g × t.
• Neglecting Air Resistance: In real-world scenarios, air resistance may slow down the object, but it is ignored in ideal free-fall calculations to simplify the analysis.