Newton's first law of motion states that when there is no net external force, an object will remain at rest or travel with a constant velocity.
When an object is moving, there is a force of friction resisting the motion, and slowing it down. To maintain a constant velocity, a person must push with a force equal to that of friction, to counteract the frictional force.
Since the pushing force cancels the friction force out, there is no net external force, and so the object moves at a constant velocity
Hope I helped! xx
P.S.: Think this question is more suited to be asked under the "Physics" section
Answer:
Water erosion refers to the removal of the top most or surface layer of soil by the flow of water. The long term effect of water erosion can be because of drastic rain fall and may be because of flood. These two reasons can adversely effect the human life. The water erosion is responsible for the removal of fertile layer of soil, therefore, the region will not be appropriate to grow vegetation. The long term effect may result in stagnation of water, therefore, long time is required so that the region gets dried. The long term accumulation of water over an agricultural field can spoil the crop production.
Prevention that can be taken to reduce long term effect of water erosion:
1. Plantation of long root bearing trees over flood prone regions and around the agricultural field: This will allow the trees to tightly hold up soil and prevent it's erosion.
2. Add rocks over the soil: In an agricultural field or flood prone area, the rocks will act as barrier for the movement of run off water, hence, will prevent water erosion. It will increase the absorption of water by soil.
3. Building of walls: This will also act as a barrier in a flood prone region and will prevent the water being added up to the agricultural land.
4.Remove soil compaction: If the soil compaction of the effected region is removed, the water retention property of the soil can be improved. Machines, animals and humans can be used for this purpose to remove the compaction of upper layer of soil.
Explanation: hope this helps.
