Final answer:
The physics question refers to the conservation of energy principle, showing how a brick transforms gravitational potential energy into kinetic energy as it falls. The brick's kinetic energy on the ground is calculated to be 39.2J, which equals its initial potential energy.
Step-by-step explanation:
The question you've asked involves the principles of mechanics, specifically within the field of physics. When an object falls under the influence of gravity, its kinetic energy increases as it loses potential energy. The kinetic energy (KE) of any object in motion is given by the formula KE = (1/2)mv², where m is the mass of the object and v is its velocity.
For the 1 kg brick falling from a 4m high roof, its initial gravitational potential energy (PE) at the top is calculated using the formula PE = mgh, where m is the mass of the brick, g is the acceleration due to gravity (9.8 m/s²), and h is the height above the ground. So, PE = 1 kg * 9.8 m/s² * 4 m = 39.2 J. When it hits the ground, all this potential energy has been converted into kinetic energy.
Given that the brick reaches the ground with a velocity of 8.85 m/s, its kinetic energy at that point can be calculated using the kinetic energy formula: KE = (1/2) * 1 kg * (8.85 m/s)² = 39.2 J. Notice that the kinetic energy just before impact is equal to the initial potential energy due to the conservation of energy principle in a system where only gravitational force does work.