Question

A car moving at $40km/h$ is to be stopped by applying brake in the next $4.0m.$ If the car weight $2000kg$ what average acceleration car?

• A. $-15.42m/s^2$
• B. $15.42m/s^2$
• C. $10.42m/s^2$
• D. $-10.42m/s^2$

Answer 1

The correct option is A $-15.42m/s^2$

Given,

$u=40km/h=\frac{40\times 1000}{60\times 60}=11.11m/s$

$v=0m/s$

$s=4m$

$m=2000kg$

From 3rd equation of motion,

$2as=v^2-u^2$

$a=\frac{v^2-u^2}{2s}$

$a=\frac{0^2-11.11\times 11.11}{2\times 4}$

$a=-15.42m/s^2$