A block of mass 1.5 kg is released from rest at the top of a rough track that…
PHYSICS · Multi-part · AP · Physics 1: Algebra-based · Force and Translational Dynamics · Force and Translational Dynamics
Problem
A block of mass 1.5 kg is released from rest at the top of a rough track that consists of two segments:
• Segment 1: A friction-free incline that drops vertically by 0.60 m.
• Segment 2: A horizontal surface with a coefficient of kinetic friction 0.25 that brings the block to rest after it has traveled a horizontal distance d.
After coming to rest, an external agent immediately pushes the block very slowly (so that its speed is negligible) straight back up the horizontal surface and then up the incline to its original starting position along the same path.
Assume the external agent applies just enough force at each point to move the block at negligible speed.
(a) Determine the work done by Earth’s gravitational force on the block while it slides down Segment 1.
(b) Determine the work done by kinetic friction on the block while it moves across Segment 2 during its initial slide until it stops. Express your answer in terms of known quantities and d.
(c) While the block is being pushed back along Segment 2 at negligible speed, calculate the work done on the block by kinetic friction. Express your answer in terms of known quantities and d.
(d) Calculate the total work done by Earth’s gravitational force on the block for the complete closed path (down the incline, across the horizontal surface, and back to the starting point). Explain your reasoning.
(e) Calculate the total work done by kinetic friction on the block for the complete closed path. Explain why this result differs from your answer in part (d).