Read Circular-Track Collisions: Use Momentum Before Timing
This short read prepares one exact NSEP pattern: spring release and collision on a circular track. Identify the physical condition before calculating.
Spring Release and Collision on a Circular Track is the central idea in this question pattern. Identify the condition in the stem before applying the method below.
Start with the physical model
Read the configuration once, state the conserved quantity or governing law, and mark any changing geometry, sign convention or limiting condition.
Build the relation
Initial momentum is zero.
B is correct. Before first collision the relative angular speed is (u+v)/R.
The proposed expression for the second collision time is not correct.
Check before selecting
Check units, sign and one limiting case. A valid result must still fit the original geometry and stated constraint.
OlympIQ exam lens
- ✓Name the governing law before using a formula.
- ✓Keep the stated geometry and direction information explicit.
- ✓Use one unit or limiting-case check.
The relative speed controls first-collision timing, but the individual speeds first come from momentum and energy together.
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