Read before you solve · 3 min
Read Accreting Bodies: Use d(mv)/dt
This short read prepares one exact NSEP pattern: falling drop with accreted mass. Identify the physical condition before calculating.
NSEP · Mechanics · 1 linked question · 100% coverage
Know this first
Falling Drop with Accreted Mass is the central idea in this question pattern. Identify the condition in the stem before applying the method below.
Study deeper: NCERT Physics · Mechanics
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
The incoming moisture is initially at rest, so momentum balance gives d(mv)/
Since dm/ dt = kt2, m(t)=m0+kt3/3
With m0 = 0.002 kg, k=0.012 kg s-3 and t=5 s, m=0.502 kg
Integrating, mv = g[m0t + kt4/12]
At 5 s, v≈12.4 m s⁻¹.
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.
OlympIQ trap
Applying ma = mg ignores the momentum required to accelerate mass that joins the drop from rest.
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