Question

4. A car increases its speed from 20 kmph to 30 kmph in 10 seconds. Its acceleration is a. 30 m/s2 b. 3 m/s2 c. 8 m/s2 d. 0.83 m/s2

Answer 1

Answer:

0.28 m/s²

Explanation:

• Initial speed of the car = u = 20 km/h. = $20\times\dfrac{5}{18}\:=\:\dfrac{50}{9}\: m/s$

• Final speed of the car = v = 30 km/h. = $30\times\dfrac{5}{18}\:=\:\dfrac{75}{9}\:m/s$

• Total time taken = 10 seconds.

Formula used :-

$\boxed{a\:=\:\dfrac{v\:-\:u}{t}}$

Putting corresponding values :-

$a\:=\: \dfrac{\dfrac{75}{9}\:-\: \dfrac{50}{9}}{10}$

=> $a\: = \:\dfrac{25}{90}$

=> a = 0.28 m/s²

Hence,acceleration of the car is 0.28 m/s².

None of the option matches the answer.

Additional points

• To change km/h into m/s, we multiply by 5/18

• To change m/s into km/h,we multiply by 18/5.