Abullet of mass 0.016 kg traveling horizontally at a speed of 280 m/s embeds itself in a block of mass 3 kg that is sitting at rest on a nearly frictionless surface. (a) what is the speed of the block after the bullet embeds itself in the block? vf= m/s (b) calculate the total translational kinetic energy before and after the collision. ktrans, i= j ktrans, f= j (c) compare the two results and explain why there is a difference. the internal energy of the block-bullet system has increased. the energy principle isn't valid for an inelastic collision. some of the momentum is lost in an inelastic collision.

(a) 1.49 m/s

The conservation of momentum states that the total initial momentum is equal to the total final momentum:

where

m = 0.016 kg is the mass of the bullet

is the initial velocity of the bullet

M = 3 kg is the mass of the block

is the initial velocity of the block

v = ? is the final velocity of the block and the bullet

Solving the equation for v, we find

(b) Before: 627.2 J, after: 3.3 J

The initial kinetic energy is (it is just the one of the bullet, since the block is at rest):

The final kinetic energy is the kinetic energy of the bullet+block system after the collision:

(c) The Energy Principle isn't valid for an inelastic collision.

In fact, during an inelastic collision, the total momentum of the system is conserved, while the total kinetic energy is not: this means that part of the kinetic energy of the system is losted in the collision. The principle of conservation of energy, however, is still valid: in fact, the energy has not been simply lost, but it has been converted into other forms of energy (thermal energy).

b would be the answer

the independent variable, or the one that is intentionally manipulated is the speed.