Analysis:
To find the initial speed of the car, we need to use the equation of motion that relates distance, initial velocity, acceleration, and time. The equation we can use is:

s = ut + (1/2)at²

Where:
- s is the distance traveled
- u is the initial velocity (speed)
- t is the time taken
- a is the acceleration

We are given:
- Distance traveled, s = 50 km = 50000 m
- Time taken, t = 4 seconds
- Acceleration, a = 5 m/s²

Calculation:
Let's substitute the given values into the equation and solve for the initial velocity:

50000 = u * 4 + (1/2) * 5 * (4)²

Simplifying the equation:
50000 = 4u + 40
50000 - 40 = 4u
49960 = 4u
u = 49960/4
u = 12490 m/s

Therefore, the initial speed of the car was 12490 m/s.

Explanation:
The initial speed of a car can be calculated using the equation of motion s = ut + (1/2)at². In this equation, we know the distance traveled, time taken, and acceleration. By substituting these values into the equation, we can solve for the initial speed.

In this case, the car traveled a distance of 50 km in 4 seconds with an acceleration of 5 m/s². To use the equation, we converted the distance from kilometers to meters (1 km = 1000 m) and substituted the values into the equation.

By simplifying the equation and solving for the initial velocity, we found that the initial speed of the car was 12490 m/s.

In conclusion, the initial speed of the car was 12490 m/s.

S=ut+1/2*at^2