NICET - Highway Construction Inspection Practice Exam

When a stone is dropped from free fall, what is the formula to calculate its final velocity after 3 seconds?

1. Vf = Vi + at

2. Vf = 0 + (9.8)t

3. Vf = 9.8 * t

4. Vf = a * t

The correct answer is: Vf = Vi + at

The formula utilized to calculate the final velocity of an object in free fall is indeed based on the principles of kinematics associated with uniformly accelerated motion. In this scenario, when the stone is dropped, its initial velocity (Vi) is zero since it is starting from rest. The acceleration (a) is due to gravity, which is approximately 9.8 m/s². The general kinematic equation for final velocity in terms of time, initial velocity, and acceleration is represented as \( Vf = Vi + at \). When applying this formula, if you substitute the known values, the equation can be specifically expressed for a time of 3 seconds as follows: \[ Vf = 0 + (9.8 \, m/s²)(3 \, s) = 29.4 \, m/s \] This confirms that the initial velocity plus the product of acceleration and time yields the final velocity after 3 seconds. Thus, it accurately represents the computation for final velocity during free fall.