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

9.72s

Step-by-step 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 * (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 =(v - u)/(t)`

Plug in the respective values ,

`\longrightarrow\sf 2m/s^2 = ( 19.4 m/s -0m/s)/(t) \\`

Simplify ,

`\longrightarrow\sf 2m/s^2 =(19.4m/s)/(t)`

Cross multiply ,

`\longrightarrow\sf t = (19.44m/s)/(2m/s^2)`

Simplify

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

Hence the required answer is 9.72s.