Question

A physics cart rolls down an inclined track. What is true about the gravitational potential energy (E_P) and the kinetic energy (E_K) of the cart?

E_P decreases and E_K increases
E_P increases and E_K decreases
They both decrease
They both increase

Answer 1

E_P decreases and E_K increases 

$E_P=mgh$

cart rolls down $\implies$ h decreases$\implies$ $E_P$ decreases

the energy conservation law: $E_P+E_K=const$

if $E_P$ decreases $\implies$ $E_K$ increases