Question

a bullet moving with 10 M per second hits a wooden plank the bullet stops when it penetrate the plank 20cm deep the retardation of the bullet

Answer 1

u=10m/s
v=0m/s
s=2/10m
So, first,we are needed to find acceleration as Acceleration is what is retardation
$We know, \\ 2as=v^{2}-u^{2} \\ 2a \frac{2}{10} =0-10^{2} \\ =>a= \frac{100}{\frac{4}{10}} ms^{-2} \\ a= -250 ms^{-2} or m/s^{2} \\ So\: retardation=-250m/s^{2}$

Answer 2

Explanation:

we have to not write negative sign because retardation means negative acceleration. So not write negative sign when answering retardation questions.