Question

What strength does a fishing line needs to stop a $10kg$ salmon (fish) swimming at $9m/s$ in a distance of $4.5m$ ? (Assume deceleration of salmon due to fishing line is constant)

• A. $70N$
• B. $80N$
• C. $90N$
• D. $100N$

Answer 1

The correct option is C $90N$

Given, Initial velocity of fish, $u=9m/s$
Final velocity of fish, $v=0m/s$ (to stop salmon)
Distance covered by fish before stopping, $s=4.5m$
Using $v^2-u^2=2as$
$0-9^2=2\left(4.5\right)\times a$
Deceleration, $\Rightarrow \overrightarrow{a}=9m/s^2$
Using Newton's second law, $|\overrightarrow{F}|=m|\overrightarrow{a}|$
$F=10\times 9=90N$