Question

A bullet m9ving at a speed of 10m/s strikes a wooden plank . The bullet penetrates the plank 2cm deep and remains embedded in it . The acceleration of the bullet is?

Answer 1

d = .02 meters

average speed = 5 m/s

time = .02 meters/ 5 m/s = .004 seconds

a = change in speed / time
= -10/.004 = -2500 m/s^2

or
d = 10 t + (1/2) a t^2
.02 = .04 + (1/2)a 1.6 *10^-5
.02 = .04 + .8*10^-5 a
.8 * 10^-5 a = -.02
a = -2500 again