Question

A motorist accelerates from rest to a velocity of $90kmh{r}^{-1}$ in $15$ seconds. What is the average acceleration of the car?

• A. $1.67m{s}^{-2}$
• B. $16.7m{s}^{-2}$
• C. $15m{s}^{-2}$
• D. $1.5m{s}^{-2}$

Answer 1

The correct option is A $1.67m{s}^{-2}$

Given:
Initial velocity $=0kmh{r}^{-1}=0m{s}^{-1}$ as he starts from rest.
Final velocity =
$90kmh{r}^{-1}=\frac{90\times 5}{18}=25m{s}^{-1}$
Acceleration is defined as the rate of change of velocity.
$a=\frac{Finalvelocity-Initialvelocity}{time}$
$a=\frac{25-0}{15}=1.67m{s}^{-2}$
Hence, the average acceleration of the car is $1.67m{s}^{-2}$