Question

A car advertisement states that a car can accelerate at 2 m/sec. The car starts from rest and accelerates to 70 km/hr. How much time does it take to accelerate to 70 km/hr.​

Answer 1

Answer:

9.72s

Explanation:

$\pink{\frak{Given}}\begin{cases}\textsf{ A car starts from rest.}\\\textsf{It has an acceleration of 2m/s ^2 .}\\\textsf{ The final velocity of the car is 70km/hr.}\end{cases}$

Here we need to find out the time that the car took to achieve the velocity of 70km/hr after starting from rest . Firstly convert the final velocity in m/s by multiplying it by 5/18 , as ,

$\longrightarrow\sf 70km/hr = 70 \times \dfrac{5}{18} m/s =\bf 19.44\ m/s$

• As we know that the rate of change of velocity is known as acceleration , so ;

$\longrightarrow\sf a =\dfrac{v - u}{t}$

Plug in the respective values ,

$\longrightarrow\sf 2m/s^2 = \dfrac{ 19.4 m/s -0m/s}{t}$

Simplify ,

$\longrightarrow\sf 2m/s^2 =\dfrac{19.4m/s}{t}$

Cross multiply ,

$\longrightarrow\sf t = \dfrac{19.44m/s}{2m/s^2}$

Simplify

$\longrightarrow\sf \boxed{\bf t = 9.72 s}$

Hence the required answer is 9.72s.