A homework answer shows a cart's roll as three snapshots of energy.
Two of them are fine. One of them cannot be right.
How do you catch the snapshot that breaks the physics?
Total each snapshot. First: 25 + 35 = 60. Second: 40 + 20 = 60. Third: 60 + 15 = 75.
The first two totals match: 60 J. The third reads 75 J: fifteen extra joules from nowhere. With no energy input, that snapshot breaks conservation.
Audit the chart above: snapshots totaling 60 J, 60 J, then 75 J, with no energy input. Which snapshot is flawed, and why?
Total each snapshot and compare along the run.
The totals read 60, 60, 75: the third total grew by 15 J.
No energy input is named, so the growth has no source.
The third snapshot is flawed: its total grew with no energy input.
The chart shows a cart's roll with no energy input. Which snapshot breaks energy conservation?
A falling KE-plus-GPE total can still be lawful: if a thermal bar grows by exactly the amount that left the mechanical stores, the full total holds.
A chart for a sliding box reads KE 50 J, GPE 30 J, thermal 0 J at one snapshot, then KE 30 J, GPE 30 J, thermal 20 J at the next. Is the chart lawful?
First total: 50 + 30 = 80. Second total: the three bars come to 80 J as well.
20 J left the mechanical stores, and the thermal bar grew by exactly 20 J.
Yes: the chart is lawful; the full total holds at 80 J.
One reading note before you audit more charts. A chart's zero level for GPE is a free choice, exactly as it is for any height. So a bin sliding across a floor can lawfully show a steady 25 J of GPE: whoever drew the chart measured heights from a lower level. The audit cares about the totals, never about where the zero was put.
Abril drew this chart for a storage bin sliding across a floor and says it could describe a real run. Is Abril right?
A falling total with NO growing thermal bar is the mirror flaw: energy has vanished from the account.
A growing total with no energy input is always a flaw, thermal included: energy does not appear from nowhere.
The chart shows a wagon's roll. Which snapshot breaks energy conservation?
The chart shows a ball's run with no energy input. Which snapshot breaks energy conservation?
Which statement correctly audits this chart of a crate's slide?
The chart shows a sled's run with no energy input. At which snapshot does the chart FIRST break energy conservation?