A BULLET FIRED INTO A BLOCK LOSES HALF ITS VELOCITY AFTER MOVING 0.9m BEFORE IT COMES TO REST, DISTANCE TRAVELLED WOULD BE ? ITS MCQ OPTIONS ARE 1.2m 0.8m 2.0m 1.6m

Asked by shreya | 27th Oct, 2013, 08:35: PM

Expert Answer:

The bullet loses half its velocity after penetrating 0.9 m into the target.
Let us say that the gun fires the bullet with force F.
 
The work done by the gun goes as change in kinetic energy of the bullet.
 
Thus, work done after penetrating 0.9 m inside the target is
 
F × (0.9 m) = ½mv2 - ½m(v/2)2 = 3/8 mv2
 
Thus, we have
 
mv2 = 2.4F
 
Now, when the bullet penetrates further distance x, the entire kinetic energy is lost. Thus, we have
 
F × (0.9 + x m) = ½mv2
 
Thus, the total distance S penetrated by the bullet inside the target is,
 

Answered by Romal Bhansali | 28th Oct, 2013, 10:03: AM

Queries asked on Sunday & after 7pm from Monday to Saturday will be answered after 12pm the next working day.