Chapter 2, Problem 5STP

To determine

To Choose: The correct option.

Answer to Problem 5STP

A correct answer is an option (B).

Explanation of Solution

Given:

The speed of the skier is $u=9\text{m/s}$

Her new speed after hill gets steeper is $v=18\text{m/s}$ .

Time taken by her to increase the speed is $t=3\text{s}$ .

Formula used:

The equation of motion can be expressed as

  $v=u+at$  ...... (1)

Here, $v,u$ , $a$ and $t$ are final velocity, initial velocity, acceleration and time respectively.

Calculation:

Rearrange the equation (1),

  $a=\frac{v-u}{t}$  ...... (2)

Substitute $18\text{m/s}$ for $v$ , $9\text{m/s}$ for $u$ and 3 s for $t$ in equation (2)

  $\begin{array}{l}a=\frac{\left(18-9\right)\text{m/s}}{3\text{s}}\\ a=\frac{9\text{m/s}}{3\text{s}}\\ \boxed{a=3{\text{m/s}}^{\text{2}}}\end{array}$

Conclusion:

Hence,the acceleration of the skier is $\boxed{a=3{\text{m/s}}^{\text{2}}}$ .