Chapter 2.4, Problem 43SSC

To determine

To Calculate: Car's position relative to start of its trip 0.25 h after it passes the gas station.

Answer to Problem 43SSC

The distance travelled by a car from start point is 23.249 km

Explanation of Solution

Given information: 

The car is moving with an average speed:

  $\begin{array}{c}85\text{km/h}\text{=}\frac{85\times 1000}{3600}\text{m/s}\\ \text{=23}\text{.61}\text{m/s}\end{array}$

Time:

  $\begin{array}{c}t=0.2\text{5 h }\\ =0.25\times 60\times 60\text{s }\\ \text{=}900\text{ s}\end{array}$

Formula used: 

Distance = speed $\times$ time

Calculation:  After driving 2 km car passes a gas station that is gas station is 2 km from starting point.

Now car continues travel for $0.25\text{ h }$ so the distance travelled by the car is given by:

Distance = speed $\times$ time

  $\begin{array}{c}s=23.61\text{m/s}\times 900\text{s}\\ =21249\text{m}\\ \text{=}\frac{\text{21249}\text{m}}{1000\text{m/km}}\\ =21.249\text{km}\end{array}$

Now the distance travelled by the car from gas station is

$\begin{array}{c}d=21.249+2\\ =23.24\text{9}\text{km}\end{array}$