Question
Only one answer is correct
A bullet moving with an initial speed of vo strikes and embeds itself in a block of wood which is suspended by a string, causing the bullet and block to rise to a maximum height h. Which of the following statements is true of the collision? o The initial momentum of the bullet before the collision is equal to the momentum of o The initial momentum of the bullet before the collision is equal to the momentum of o The kinetic energy of the bullet and block immediately after the collision is equal to the bullet and block at the instant they reach the maximum height h the bullet immediately after the collision the potential energy of the bullet and block at the instant they reach the maximum height h. O The initial kinetic energy of the bullet before the collision is equal to the potential energy of the bullet and block when they reach the maximum height h. The initial kinetic energy of the bullet before the collision is equal to the kinetic energy of the bullet and block immediately after the collision
Explanation / Answer
It will b ethird option, that is
The kinetic energy of the block+bullet after collision will be equal to the potiential energy of block+bullet at height h.
Second option also seems right, but if you closely reads it, it only talks about momentum of the bullet. While there will be an external force on the bullet so it's momentum will not be conserved.
Momwntum of block+bullet system will be conserved, i.e inital momentum of bullet= final momentum of block+bullet
WE know the energy always remains constant, so option 3 will be right.