- #1
CGandC
- 326
- 34
Homework Statement
( The following problem is taken from kleppner's " Introduction to mechanics" )
( The question in the book talks about the velocity but my confusion is related to the Energy )
Homework Equations
Conservation of Mechanical energy : Ef - Ei = 0
Consevation of Momentum : Pf - Pi = 0
The Attempt at a Solution
If I can assume the time which mass 'm' reaches the edge of the block is very small , and if I also assume both masses ( m , M ) are pretty small , then the total impulse can be approximately zero and the total momentum difference is conserved , so that :
where ' V ' is the velocity of the larger object 'M'
and ' v ' is the velocity of the smaller object 'm'
So far all is correct.
and only used it for mass 'm' ( the normal force does no work since it's constantly prependicular to the
cube's path and the only work done on mass 'm' is from gravity ) so that :
Eventually getting ( my answer ) :
However , this is not the correct answer , because in the answers they included both the energies by mass 'm' and mass 'M' , so that:
Eventually getting ( the correct answer ) :