Answer:
The velocity of the ball the instant before it strikes the ground is 30m/s
Given the data in the question
Since the ball was initial at rest before it was dropped by the child
Initial velocity;
Time taken for the ball to hit the ground;
Final Velocity;
To find the velocity of the ball the instant before it hits the ground
We use the First Equation of Motion:
Where v is the final velocity, u is the initial velocity, t is time and a is the acceleration.
Now, since the ball was thrown from a particular height (window), it is under gravity and acceleration due to gravity;
Hence, the equation becomes;
We substitute our values into the equation
Therefore, the velocity of the ball the instant before it strikes the ground is 30m/s.
Explanation: