[1] Circle the answer that correctly completes the sentence correctly. (a) A truck is accelerated in the forward direction by the force of the ( truck's tire on the ground ground on the truck's tire | none of the above ). (b) A rough surface can exert a(n) ( normal | tangential | all of the above | none of the above) force. (c) Many of the great rivers in the world have a tendency to flow from the pole towards the equator. Over time as they carry sediment towards the equator, the length of the earth's day will ( increase | decrease | not change ) . (d) For the graph of the potential energy of a particle as a function of x, the particle will have the greatest speed where the potential energy graph is ( maximum | | steepest | 0 | minimum | none of the above ) (e) For an object in circular motion ( centripetal | tangential | all of the above | none of the above ) acceleration will change the direction of the velocity vector. Statements (f) through (h) refer to the figure below which shows the position of an object as a function of time. Circle all the times that complete the statement correctly