[a bullet weighing 50gm hits a 10cm

Question

wall with velocity 100ms-1 and comes out of the wall. If the frictional force on the bullet
while in the wall is assumed to be a constant 2000N then with what velocity does the bullet
come out of the wall?

Answer 1

v = V0 + a * t
F = m * a
s = .5 * a * t^2
where s = 0.01 m
V0 = 100 m / s
m = 0.5 kg
F = 2000 kg m/(s^2)
solving f=ma for a :
a = f/m = -2000/0.05 m/(s^2) = -40000 m/(s^2)
solving s = .5at^2 for t :
2s = at^2
2s/a = t^2
t = square root(2s/a)
t=square root (2 * 0.01m) / -40000 m/(s^2)
t = 0.0000005 s

so
v =100 m/s - 40000 m/(s^2) * .0000005 s * .0000005 s
v = 100 m/s - 0.00000010 m /s
v = 99.99999999 m/s

Answer 2

P.S. forgot to take square root in time
calculation. Should be t = .0007s
so
v = 100 - 40000 * .0007 * .0007
v = 100 - .02
v = 99.98 m /s

Answer 3

The given answer is root over 2000