A laboratory cart of negligible friction contains a compressed spring positioned…
PHYSICS · Multi-part · CBSE · Physics · Laws of Motion · Laws of Motion
Problem
A laboratory cart of negligible friction contains a compressed spring positioned between two identical 0.50kg blocks that touch the spring’s ends. A thin string wrapped around the spring keeps it compressed. The cart is initially at rest on a horizontal, frictionless track. At t=0s the string is cut, allowing the spring to push the blocks apart for a very brief interval Δt, after which the spring is completely relaxed and no longer in contact with either block. Ignore the mass of the spring.
(1) Part 1: (a) Consider the system consisting of both blocks and the spring. During the interval Δt, identify all forces that are external to this system. Justify your answer.
(2) Part 2: (b) For the same interval Δt, consider instead the system consisting of only the left block. Identify the forces that are external to this reduced system. Explain how you decided.
(3) Part 3: (c) For each of the two systems defined in parts (a) and (b), indicate whether the net impulse delivered to that system during Δt is zero or non-zero. Provide reasoning based on your force identification.
(4) Part 4: (d) Using your conclusions, compare the change in linear momentum of the whole-cart system (both blocks together) with the change in linear momentum of the left block alone over the interval Δt. State which, if either, is zero and support your answer.