Read the following case and answer the questions given below:
A school is testing a new emergency braking system for its buses. During the test, a bus of mass \(2000\ kg\) is moving at a speed of \(18\ m/s\) on a straight road. When the driver notices an obstacle ahead, the emergency braking system is activated.
The brakes perform negative work on the bus, reducing its kinetic energy. Engineers are interested in understanding how the bus's kinetic energy changes during braking and how work done by the brakes affects the motion of the bus.
Assume that air resistance is negligible and the braking force acts uniformly.
Answer the following questions based on the information given.
1. What is the initial kinetic energy of the bus?
2. If the bus's speed is reduced to half its original value, what fraction of its original kinetic energy remains?