Bullet hitting stationary Target.

[Adarshaero]

A bullet of 0.005 kg traveling at 20m/s penetrates deeply into a fixed target and is brought to rest in 0.01 sec. The distace through which it penetrates is:

I used,

acceleration= V/t
= 20/.01
a = 2000 m/sec sq

Distace covered = Ut+0.5 at^2
= 20*0.01+0.5*2000*(o.o1)^2
S= 30cm.

Is it correct or any other solution is possible..?

 

[willem2]

The initial speed and the acceleration have opposite directions.

 

[Adarshaero]

@willem2:

How is tat? can you please elaborate.

 

[gneill]

Does the bullet slow down or speed up as it moves through the block? So is acceleration positive or negative?

 

[Adarshaero]

Acceleration reduces as the bullet enters the target.

 

[Adarshaero]

so acceleration is negative...

 

[gneill]

so acceleration is negative...

The velocity reduces as it passes through the target. So yes, acceleration is negative (in the direction opposite to the velocity).

 

[Adarshaero]

I understand ur point. So is the approach right? And how about answer?

 

[gneill]

The approach is fine. How about the answer? Have you calculated one with the new knowledge about the acceleration direction?