Question

A man shoot a bullet with a speed of 10m/s which just penetrates a plank of wood . With what speed should be shoot the bullet so that it passes 10 similar planks?

Answer 1

Hey mate!

Here's your answer!!

Energy at 10m/sec = 100m/2 kgm²/s², energy reuired to pass through 10 planks is 1000 m/2 kgm²/s².

Mass remaining same,
v = √1000 = 10√10m/s.

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#BE BRAINLY

Answer 2

By third equation of motion v2=u2+2as

v=0 , u= 10

0=100-2as

100/2s=a

a =50/s ____(1)

Again by third equation of motion

v2=u2 +2as

0=u2 -2*50/s ( from equation 1)

u2 = 1000

So u = 10√10m/s