Given :
Initial velocity , u = 0 m/s² .
To Find :
The acceleration of the cart.
Solution :
Since, acceleration is constant.
Using equation of motion :

Putting, t = 1 s and x = 4 m in above equation, we get :

Therefore, the acceleration of the cart is 8 m/s².
The correct answer would be the first option. The process that would need more energy would be vaporizing 1 kg of saturated liquid water at a pressure of 1 atmosphere. This can be seen from the latent heat of vaporization of each system. For the saturated water at 1 atm, the latent heat is equal to 40.7 kJ per mole while, at 8 atm, the latent heat is equal to 36.4 kJ per mole. The latent heat of vaporization is the amount of heat needed in order to vaporize a specific amount of substance without any change in the temperature. As we can observe, more energy is needed by the liquid water at 1 atm.