What kinds of energy are involved in the schematic diagram of Newton's steam car

What kinds of energy are involved in the schematic diagram of Newton's steam car

Chemical energy is converted into internal energy and internal energy into mechanical energy

When Xiaoying is shopping in the supermarket, she pushes a small car with 5N horizontal force to move in a straight line at a constant speed on the horizontal ground. Suddenly, Xiaoying finds a child in front of her. She immediately uses 10N horizontal force to pull the car backward to slow it down. In the process of deceleration, the resultant force of the car is______ N (assuming the resistance of the car is constant)

Using 5N horizontal force to push a car on the horizontal ground to do uniform linear motion, the car is in a state of balance, from the balance condition: F = F1 = 5N; when she uses F2 = 10N force to pull back the car, the contact surface between the car and the ground does not change, the car pressure on the ground does not change, so the car friction f = 5N does not change