Question

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Answer 1

$\mathbb {\huge {\orange {\boxed {ANSWER }}}}$

Initial velocity of the bullet = 20m/s

Final velocity of the bullet = 0m/s (as the bullet stops after 5cm)

Distance travelled by the bullet in the meterial = 5cm

For acceleration, formula will be =

$\large { {v}^{2} = {u}^{2} + 2aS}$

where,

v = final velocity

u = initial velocity

a = acceleration

S = Distance

Now, according to this,

$\large { {0}^{2} = {20}^{2} + (2 \times a \times 5)}$

= $\large { {0}^{2} = {20}^{2} + (10a)}$

= $\large { 0 = 400 + (10a)}$

= $\large {- 10a = 400 }$

= $\large {- 10a = 400 }$

= $\large {- a = \frac{400}{10} }$

= $\large {- a = 40 }$

= $\large {a = -40 }$

Thus, negative acceleration is -40m/s² or retardation is 40m/s².