# Calculating the Speed of a Falling Object

## How can we determine the speed of a penny when it hits the ground if it is thrown downward off of a 100 m building with an initial velocity of 15 m/s?

To calculate the speed of the penny when it hits the ground, we need to consider the initial velocity, acceleration, and distance traveled. In this scenario, the penny is thrown downward with an initial velocity of 15 m/s and a distance of 100 m. The acceleration due to gravity is 9.8 m/s², which will affect the speed of the penny as it falls.

Using the equation of motion v^2 = u^2 + 2as, where v is the final velocity, u is the initial velocity, a is the acceleration, and s is the distance traveled, we can plug in the values to find the final speed of the penny. In this case, u is -15 m/s, a is -9.8 m/s², and s is 100 m.

After solving the equation, we discover that the speed of the penny when it hits the ground is approximately 45.9 m/s. This calculation takes into account the negative initial velocity and the acceleration due to gravity acting on the penny as it falls.

Understanding how to calculate the speed of a falling object is important in physics and helps us comprehend the effects of gravity on moving bodies. By applying the equations of motion, we can determine the final velocity of objects in free fall scenarios like the one involving the penny falling from a building.