Final answer:
Large grains in a stream collide and break other grains into smaller pieces through a process called abrasion. This process is important in geological processes such as weathering and erosion.
Step-by-step explanation:
Large grains in a stream can collide with other grains and break them into smaller pieces through a process called abrasion. This is a common occurrence in geological processes such as weathering and erosion. When rocks are exposed to external forces like water movement, they can break apart into smaller fragments due to the impact of collisions between grains.
For example, in a river or stream, as water flows and carries sediment, the movement of large grains can cause them to collide with smaller grains. These collisions can cause the larger grains to break into smaller pieces, resulting in the creation of smaller particles like gravel, sand, and clay.
Overall, this process of grain collision and breaking into smaller pieces plays a significant role in shaping the landscape and the formation of different types of sedimentary deposits.