Question

Hair grows at an average speed of 3x10^-9 m/s. how long does it take to get to 10cm? note: 1 yr = 3.156 × 10^7 s.

Answer 1

Given that the growth speed of hair is 3 x 10^-9 m/s.

We have to determine how long would it take to get to 10 cm.

It is known that t = d/s.

Here, d = 10 cm = 0.1 m and s = 3 x 10^-9 m/s. So,

$\begin{gathered} t=\frac{0.1}{3\times10^{-9}} \\ t=\frac{0.1\times10^9}{3} \\ t=\frac{10}{3}\times10^8 \\ t=3.33\times10^8\text{ seconds} \end{gathered}$

We know that 1 yr = 3.156 × 10^7 s. So, the time taken (in years) is:

$\frac{3.33\times10^8}{3.156\times10^7}=1.055\times10=10.55\text{ years}$

Thus, it will take 10.55 years to grow the hairs to 10 cm.