To solve this question, we can use the equation for kinetic energy: KE = 1/2mv^2. In this equation, m represents the mass of the object and v represents its velocity.
The question states that the semi-truck decreases its speed from 10 m/s to 5 m/s, so we need to compare the kinetic energy before and after the decrease in speed.
Let's assume the mass of the semi-truck remains constant. So, m (mass) can be canceled out from the equation.
Now, let's calculate the initial kinetic energy:
KE_initial = 1/2 * m * (10 m/s)^2
And the final (new) kinetic energy:
KE_final = 1/2 * m * (5 m/s)^2
Now we can compare the initial and final kinetic energy values to determine which option is correct.
Let's calculate the ratio between the final and initial kinetic energy:
KE_final / KE_initial = [1/2 * m * (5 m/s)^2] / [1/2 * m * (10 m/s)^2]
= (5 m/s)^2 / (10 m/s)^2
= 25 / 100
= 1/4
Therefore, the ratio of the final kinetic energy to the initial kinetic energy is 1/4 or 1:4.
Hence, the correct answer is option (d) - The new Kinetic Energy is 1/4 its old Kinetic Energy.