Question

A block of mass $1\ \text{kg}$ is kept on an ice surface. When a velocity of $4\ \text{m/s}$ is given to it, it stops by friction in $5\ \text{s}$. The coefficient of friction is $\left[g = 10\ \text{m/s}^2\right]$

• A. $0.06$
• B. $0.04$
• C. $0.02$
• D. $0.08$

Hint:

When friction is the only force causing retardation, use $a = \mu g$.

Answer 1

The Correct Option is D

Step 1: Calculate acceleration.
Initial velocity $u = 4\ \text{m/s}$, final velocity $v = 0$, time $t = 5\ \text{s}$.
\[ a = \dfrac{v - u}{t} = \dfrac{-4}{5} = -0.8\ \text{m/s}^2 \] Step 2: Relation between acceleration and friction.
\[ a = \mu g \] Step 3: Calculate coefficient of friction.
\[ \mu = \dfrac{0.8}{10} = 0.08 \]