Question

A stone of $1Kg$ is thrown with a velocity of 20 $m{s}^{-1}$ across the frozen surface of a lake and comes to rest after traveling a distance of $50m$. What is the force of friction between the stone and the ice?

• A. $4N$
• B. $2N$
• C. $3N$
• D. $5N$

Answer 1

The correct option is A $4N$

By energy conservation;

Work done by friction = Kinetic Energy

$f\times 50=\frac{1}{2}m{v}^2$

$f\times 50=\frac{1}{2}\times 1\times (20{)}^2=\frac{1}{2\times 50}\times 400=4N$