Question

A bullet of mass 10 gram travelling horizontally with a velocity of 150 M per second strikes and stationary wooden block and comes to rest is 0.03 second calculate the distance of Pareshan of the bullet into the block also calculate the magnitude of the force exerted by the wooden block on the bullet

Answer 1

As work = Force * displacement

 Or W = F * s

It can be also written as W = m * a * s

Now, velocity of bullet before hitting the tree is u and is 500 m s-1 and after hitting the tree is v and is 400 m s-1

Apply the 3rd equation of motion , v 2 = u 2 + 2 a s

here , velocity decreases so body retards and equation also changes as v 2 = u 2 - 2 a s

put u = 500 m s-1  and v = 400 m s-1

=> ( 400 )2 = ( 500 )2  - 2 a s

=> 2 a s = ( 500 )2 - ( 400 )2

=> 2 a s = ( 500 - 400 )( 500 + 400 )  { from the identity in maths a 2 - b2 = ( a + b )(a - b ) }

=> 2 a s = 100 * 900

=>  a s = 45000 ,let this equation be named as ( 1 ) Or  a s = 45000 ............. ( 1 ) 

Now W = m * a * s

as m and a * s are given 

put these given values in the above given equation

 So W = ( 20 / 1000 ) { as work is measured in J ,so for Joules mass is considered in kgs } * 45000

=> W = 20 * 45

=. W = 900 J

So ,work done by the bullet is 0.9 kJ or 900 J

Answer 2

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