Question

A bullet of mass 100 g strikes a wooden block at 50 m/s and penetrates inside by 20 cm.

Calculate the retardation of the bullet and the time taken for the bullet to come to rest.​

Answer 1

Answer:

Retardation = 6250 m/s

Time taking for rest (t) =0.4 second

Explanation:

Given that,

mass of bullet =100 g. =0.1 kg.

at rest : v= 0 and u =50 m/s

and penetration =20 cm. =0.2 m.

retardation = a = ?

1st ) By 3rd law of motion,

v^2 - u^2 = 2as

0^2 - 50^2 = 2× -a ×0.2

2500= 2× -a ×0.2

-a = 2500/(2×0.2)

-a =2500/0.4=25000/4

-a= 6250 m/s

(-) mark shows that it is retardation.

2nd)

By 1st law of motion,

v = u -at ("-" mark for retardation)

0 = 50^2 - 6250 × t

0 = 2500 - 6250 × t

Or

6250 × t = 2500

t = 2500/6200= 25 /62 =0.4 s.

Answer 2

Answer:

I think 6250 m/s. is right answer.