Question

Moving water, like that of a river, carries sediment as it moves along its bed. The faster the water flows, the more sediment that is carried and the larger the sediment particles. As the river slows down, the heavier particles of the load will settle out. How can you explain the particle movement based on Newton's laws of motion?
A) An object remains at rest until a force acts on it.
B) For every action there is an equal and opposite reaction.
C) The greater the force of the water, the faster the particle accelerates.
D) The water and the particle exert a gravitational attractive force on each other.

Answer 1

Explanation :

Newton's laws of motion tells us the work of gravity. In this case, initially the sediments are at rest. As the faster water flows, the more sediments carries out with larger sediment particles and when the flow of water is less, the heavier particle will settle out. This implies that the greater the force of water, the faster the particle accelerates.

Answer 2

Correct option: A

An object remains at rest until a force acts on it.

As the water moves faster, it applies greater force on the sediment, which over comes the frictional forces between the bed and the sediment. So, when the river flows faster, more and larger sediment particles are carried away. When the flow slows down, the river couldn't apply enough force on the larger sediments which can overcome the frictional force between the sediment and the river bed. So, the net force on the heavier particles become zero. Hence, the heavier particles of the load will settle out.