Answer;
A barrier, a surface or a boundary
Explanation;
Reflection is the property waves that occurs due to the bouncing back of a wave after it strikes a barrier.
Reflection involves change in direction of a wavefront at an interface between two different media such that the wavefront returns into the medium from which it originated. In other words, the direction of the wave changes when they bounce of a barrier or a surface.
Answer:


Explanation:
The bulldozer is moving the rocks as one system, the weigth for the complete system is:

From newton´s second law the acceleration can be related to the force by:

on the middle rock we have the force F12 from the first to the middle rock on the direction of movement and F32 from the las rock to the middle rock on the opposite direction of movement.
For the last rock to accelerate at the same rate it must be subjected to a force:

This equals the force F32 on the opposite direction. the resultant force on the middle rock to mantain this acceleration should be:

The sum of all the forces applied to the middle rock is:

Solving for F12:

Freeze wedging<span> is caused by the repeated freeze-thaw. </span>Frost wedging<span> occurs as the result of 9 % expansion of water when it is converted to ice. Cracks filled with water are forced further apart when it freezes. cycle.</span>
Answer: Last option (total energy always remains constant)
Explanation:
The Law of Conservation basically states that energy cannot be created or destroyed. Only changed from one form to another (potential, kinetic, chemical, etc.) so it makes sense that the net energy is unchanging.
A is the correct answer to the question