Question

A bullet of mass 70 g moving with an initial velocity 100 m s-1 strikes a wooden block and comes to rest after penetrating a distance 25 cm in it. Calculate: (i) Initial momentum of the bullet, (ii) Final momentum of the bullet, (iii) Retardation caused by the wooden block and (iv) Resistive force exerted by the wooden block.

Answer 1

Explanation:

initial momentum=7000

final momentum=0

retardation=-200m/s^2

Answer 2

Answer:

:( Given:

Mass of the bullet :

= 70 g or 0.07 kg

Initial velocity of the bullet :

= 100 m s-¹

Final velocity of the bullet :

= 0 m s -¹

On the wooden block the bullet cover penetrating distance till coming to rest is :

= 25 cm or 0.025 m

:( To find:

(i) Initial momentum of the bullet

(ii) Final momentum of the bullet

(iii) Retradation caused by the wooden block

(iv) Resistive force exerted by the wooden block

:( Taken:

To find initial momentum:

I = mv

Where,

I = Initial momentum

m = Mass of the bullet

v = Initial velocity of the bullet

To find final momentum:

F = mu

Where,

F = Final momentum

m = Mass of the bullet

u = Final velocity of the bullet

To find the retradation caused on the wooden block:

R = v² = u² + 2 as

Where,

R = Retradation

v² = Initial velocity

u² = Final velocity

a = Acceleration

s = Penetrating distance travelled in the wooden block

To find the resistive force exerted by the wooden block :

F = m×a

Where,

F = Force

m = Mass of the bullet

a = Acceleration

:( Solution:

(i) To find Initial momentum:

$\bold\purple{Taken,I=mu}$

>> I = 0.07 kg × 100 m s-¹

>> I = 7 kg . m/s

(ii) To find the final momentum:

$\bold\purple{Taken,F=mv}$

>> F = 0.07 kg × 0

>> F = 0 kg . m/s

(iii) To find the retradation caused on the wooden block:

$\bold\purple{Taken,v²=u²×2as}$

>> (0)²=(100)²×2×a×0.025m

>> (0×0)-(100×100)=0.050a

>> 0-10000=0.050a

>> -10000=0.050a

>> -10000/-0.050=a

>> 5000 m/s²=a

(iv) To find the resistive force exerted of the wooden block:

$\bold\purple{Taken,F=ma}$

>> F = 0.07kg×5000 m/s²

>> F = 350 N

:( Answer:

(i) Initial momentum of the bullet:

= 5 kg . m s-¹

(ii) Final momentum of the bullet:

= 0 kg . m s-¹

(iii) Retradation caused on the wooden block:

= 5000 m/s²

(iv) Resistive force exerted on the wooden block:

= 250 N

:( Additional information:

To find the acceleration:

$\bold{A=\frac{V1-V}{T}}$

Where,

A = Acceleration

V1 = Final velocity

V = Initial velocity

T = Time

To find the velocity:

$\bold{V=\frac{D}{T}}$

Where,

V = Velocity

D = Displacement

T = Time

First equation of motion:

$\bold{Vf=Vi+at}$

Where,

Vf = Final velocity

Vi = Initial velocity

a = Acceleration

t = Time

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