Arifle with a barrel length of 60 cm fires a 10 g bullet with a horizontal speed of 400 m/s. the bullet strikes a block of wood and penetrates to a depth of 12 cm. a. what resistive force (assumed to be constant) does the wood exert on the bullet? . b. how long does it take the bullet to come to rest? . c. draw a velocity verses time graph for the bullet in the wood.

consider the motion of bullet as it penetrates through the block

v₀ = initial velocity of the bullet  = 400 m/s

v = final velocity of the bullet  = 0 m/s

d = distance traveled = 12 cm = 0.12 m

a = acceleration = ?

Using the equation

v² = v₀² + 2 a d

0² = 400² + 2a (0.12)

a = - 6.67 x 10⁵ m/s²

m = mass of the bullet = 10 g = 0.010 kg

The resistive force is given as

f = ma

inserting the values

f = (0.010) (- 6.67 x 10⁵ )

f = - 6670 N

b)

t = time taken by the bullet

using the equation

v = v₀ + a t

0 = 400 + (- 6.67 x 10⁵ ) t

t = 6 x 10⁻⁴ sec

c)

the duration of a photographic flash is related to an rc time constant, which is 0.100 μs for a certain camera.