A trolley is initially at rest at X. It moves down to Y and finally stops at Z. Which row could summarise the energy changes during this process?
- AX to Y: $\text{PE} \rightarrow \text{KE}$; Y to Z: $\text{KE} \rightarrow \text{PE}$
- BX to Y: $\text{PE} \rightarrow \text{KE}$; Y to Z: $\text{KE} \rightarrow \text{PE} + \text{heat}$
- CX to Y: $\text{PE} \rightarrow \text{KE} + \text{heat}$; Y to Z: $\text{KE} \rightarrow \text{PE}$
- DX to Y: $\text{PE} \rightarrow \text{KE} + \text{heat}$; Y to Z: $\text{KE} \rightarrow \text{PE} + \text{heat}$