Chapter 2, Problem 13STP

To determine

The acceleration of a car in ${\text{m/s}}^{\text{2}}$ .

Answer to Problem 13STP

The acceleration of the car is $\boxed{a=-11.11{\text{m/s}}^{\text{2}}}$ .

Explanation of Solution

Given:

The initial velocity of the car is $u=40\text{km/h}$ .

Time is $t=5\text{s}$ .

Final velocity is $v=0\text{m/s}$ .

Formula used:

The equation for the final velocity of the car is

  $v=u+at$  ...... (1)

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

Calculation:

Rearrange the equation (1)

  $a=\frac{v-u}{t}$  ...... (2)

Substitute $40\text{km/h}$ for $u$ , $0\text{km/h}$ for $v$ and 5 s for $t$ in equation (2)

  $\begin{array}{l}a=\frac{0\text{km/h}-40\text{km/h}}{5\text{s}}\\ a=\frac{-\left(40\text{km/h}\right)\left(\frac{1000\text{m}}{1\text{km}}\right)\left(\frac{1\text{h}}{3600\text{s}}\right)}{5\text{s}}\\ \boxed{a=-11.11{\text{m/s}}^{\text{2}}}\end{array}$

Conclusion:

Hence,the acceleration of the car is $\boxed{a=-11.11{\text{m/s}}^{\text{2}}}$ .