4. In 5 seconds, an automobile speeds from [tex]18 \, \text{km/hr}[/tex] to [tex]36 \, \text{km/hr}[/tex]. What is the acceleration of the automobile in [tex]m/s^2[/tex]?

A. [tex]1 \, \text{m/s}^2[/tex]
B. [tex]3 \, \text{m/s}^2[/tex]
C. [tex]2 \, \text{m/s}^2[/tex]
D. [tex]4 \, \text{m/s}^2[/tex]



Answer :

Let's solve the problem step-by-step.

Step 1: Convert the speeds from km/h to m/s

Given:
- Initial speed: [tex]\(18 \, \text{km/h}\)[/tex]
- Final speed: [tex]\(36 \, \text{km/h}\)[/tex]

To convert from km/h to m/s, use the conversion factor: [tex]\(1 \, \text{km/h} = \frac{1}{3.6} \, \text{m/s}\)[/tex].

So, for the initial speed:
[tex]\[18 \, \text{km/h} = 18 \times \frac{1}{3.6} \, \text{m/s} = 5 \, \text{m/s}\][/tex]

For the final speed:
[tex]\[36 \, \text{km/h} = 36 \times \frac{1}{3.6} \, \text{m/s} = 10 \, \text{m/s}\][/tex]

Step 2: Calculate the change in speed

Change in speed (Δv) = Final speed - Initial speed
[tex]\[Δv = 10 \, \text{m/s} - 5 \, \text{m/s} = 5 \, \text{m/s}\][/tex]

Step 3: Calculate the acceleration

Acceleration [tex]\(a\)[/tex] is defined as the change in speed divided by the time taken.

Given:
- Change in speed [tex]\(Δv = 5 \, \text{m/s}\)[/tex]
- Time [tex]\(t = 5 \, \text{s}\)[/tex]

So, acceleration [tex]\(a\)[/tex] is:
[tex]\[a = \frac{Δv}{t} = \frac{5 \, \text{m/s}}{5 \, \text{s}} = 1 \, \text{m/s}^2\][/tex]

Conclusion:

The acceleration of the automobile is [tex]\(1 \, \text{m/s}^2\)[/tex].

Therefore, the correct answer is:
a. [tex]\(1 \, \text{m/s}^2\)[/tex]