Question

The plot depicts the net force acting on a sled on a frictionless track of ice as it is displaced from the starting point. The sled has mass $10.0kg$.
If the sled was momentarily at rest when it was $x=0m$ away from where it started, what was its speed at $x=4m$?

• A. $0m/s$
• B. $1m/s$
• C. $\sqrt{2}m/s$
• D. $2m/s$
• E. $4m/s$

Answer 1

The correct option is C $\sqrt{2}m/s$

Given : $m=10.0$ kg $u=0$ m/s

Area under F-x graph gives amount of work done due to that force.

$\therefore$ Work done in moving from $x=0$ m to $x=4$ m $W=$Area $=\frac{1}{2}\times 5\times 4=10$ J

Work-energy theorem : $W=\Delta K.E=\frac{1}{2}m{v}^2-\frac{1}{2}m{u}^2$

$\therefore$ $10=\frac{1}{2}\times \left(10.0\right)v^2-0$ $⟹v=\sqrt{2}$ $m/s$