Introduction:
To find the work done in increasing the speed of a car from 36 km/h to 72 km/h, we need to understand the concept of work, which is defined as the product of force and displacement. In this case, the force is the net force applied to the car, and the displacement is the distance traveled by the car.

Given Information:
- Mass of the car = 1000 kg
- Initial speed = 36 km/h
- Final speed = 72 km/h

Converting Speed to m/s:
To calculate the work done, we need to convert the speeds from km/h to m/s as the SI unit of force is Newton (N) and the SI unit of displacement is meter (m).
- Initial speed = 36 km/h = 10 m/s (approx)
- Final speed = 72 km/h = 20 m/s (approx)

Calculating Change in Kinetic Energy:
The work done in increasing the speed of the car is equal to the change in its kinetic energy. The kinetic energy of an object is given by the equation: KE = 0.5 * mass * velocity^2.
- Initial kinetic energy (KEi) = 0.5 * 1000 kg * (10 m/s)^2 = 50,000 J
- Final kinetic energy (KEf) = 0.5 * 1000 kg * (20 m/s)^2 = 200,000 J

Calculating Work Done:
The work done (W) in increasing the speed of the car can be calculated by subtracting the initial kinetic energy from the final kinetic energy:
- Work done (W) = KEf - KEi = 200,000 J - 50,000 J = 150,000 J

Conclusion:
The work done in increasing the speed of the car from 36 km/h to 72 km/h is 150,000 Joules. This means that 150,000 Joules of energy was transferred to the car to increase its speed.