The mechanical weathering is a type of weathering where physical force is included into the breaking up of the rocks. The plants and the animals are both causing this type of weathering with their actions. The plants can cause mechanical weathering with their roots, as they grow and surround a rock, they are able to create such a pressure that they can break the rock apart. Also, as their trunks are getting bigger, if there's rocks right next to them, the pressure from the growing of the trunk will crack the rocks. The animals are able to move the rocks, as well as pushing them, or even deliberately throwing them, so they manage to break up parts of them and cause mechanical weathering.
The bucket is moving at a constant speed of 2m/s Therefore F=ma is 0 N for this to be correct the magnitude of the force exerted by the rope must be equal to the weight of the bucket which is 5 N