A level physics edexcel specimen paper 1 question

A bullet is fired into a block of wood. why would both the kinetic energy and momentum not be conserved?

A bullet is fired into a block of wood. why would both the kinetic energy and momentum not be conserved?

A bullet is fired into a block of wood. why would both the kinetic energy and momentum not be conserved?

Like others have said, this is an inelastic collision so KE isn't conserved. Some of the energy is transferred to thermal through the friction of the wood.

However momentum is always conserved when there are no external forces applying on the system hence there is no acceleration.

This question is asking why momentum isn't conserved and that is due to an external force, such as a drag (resistance to the motion of the bullet) and possibly if the wooden block was on a rough surface, a frictional force would be causing a deceleration to it.

Quite simply, because air resistance and possibly resistance to the motion of the block is causing an acceleration hence the velocity will not be constant hence momentum isn't conserved. KE is also lost to sound, heat (Due to friction) as this is not an elastic collision.

Nah momentum is always conserved, mistake in the question, edexcel released an erratum notice

Momentum is only conserved when external forces (such as drag) are not applying on the system. It's not always conserved.

If it said in the question resistances to motion is negligible, then you're point would be valid, but this isn't case since he hasn't posted the full question.