Step 1: Write expression for linear momentum.
\[
p = mv
\]
Step 2: Use condition of constant momentum.
If momentum is constant:
\[
mv = \text{constant}
\]
Step 3: Express velocity in terms of mass.
\[
v = \frac{p}{m}
\]
Step 4: Analyze the relation.
Velocity is inversely proportional to mass:
\[
v \propto \frac{1}{m}
\]
Step 5: Identify graph nature.
An inverse relation between two variables gives a rectangular hyperbola.
Step 6: Interpret physically.
As mass increases, velocity decreases such that their product remains constant.
Step 7: Final answer.
\[
\boxed{\text{Hyperbolic decreasing curve}}
\]