Chapter 5, Problem 8STP

To determine

To Choose: The correct option.

Answer to Problem 8STP

C. The required stopping distance Sukey is 6.8 m.

Explanation of Solution

Given:

Mass of her bicycle together m = 9.5 kg

Speed of bicycle v = 25 km/h = 6.94 m/s

Coefficient of friction is $\mu =0.36$

Formula used:

The relation between force and normal reaction N is

  $\begin{array}{c}ma=N\mu \\ ma=0.36mg\\ a=0.36\times 9.81\\ =3.53{\text{ m/s}}^2\end{array}$

Calculation:

Distance cover before stop is

  $\begin{array}{c}{v}^2=u^2-2as\\ 0^2={\left(6.94\right)}^2-2\left(3.53\right)s\\ \Rightarrow s=\frac{{\left(6.94\right)}^2}{2\left(3.53\right)}\\ =6.83\text{ m}\end{array}$

Conclusion:

The stopping distance Sukey require is 6.83 m.

Hence, the correct option is (c).