A small cart of mass is released from rest at point A on a track that is otherwise…
PHYSICS · Multi-part · CBSE · Physics · Work, Energy and Power · Work, Energy and Power
Problem
A small cart of mass 0.80kg is released from rest at point A on a track that is otherwise frictionless except for a rough horizontal section CD. Point A is 2.0m above the lowest point B. The cart descends to B, then rises to point C at a height of 1.5m above B. Immediately after passing C, it enters the 0.40m-long rough section CD (coefficient of kinetic friction μk=0.15) located at the same height as C. After leaving D, the track is friction-free again and the cart climbs a final hill to point E where it momentarily comes to rest.
Four checkpoints are defined:
• A – initial release
• C – just before entering the rough section
• D – just after leaving the rough section
• E – final rest point
(a) For each checkpoint, draw and label a qualitative energy bar chart that includes gravitational potential energy, kinetic energy, and thermal energy. Use the same total bar-height scale for all checkpoints.
(b) Identify the stage of the motion during which the greatest mechanical energy loss occurs and explain your reasoning in terms of the interactions between the cart and its environment.
(c) Suppose the length of the rough section were doubled while all other conditions remained the same. Without performing numerical calculations, describe how each bar in the chart for point D would change and explain why.