Final answer:
To determine the velocity at t = 5 s and the time at which velocity is zero for a block on a frictionless inclined plane, the precise form of the varying force P over time is needed. Without this information, the problem cannot be solved.
Step-by-step explanation:
The student's question concerns the calculation of velocity and time for a block sliding on a frictionless inclined plane. Since the force acting on the block (P) varies with time as per a graph, the problem would usually need a description of the force's variation over time to solve for velocity and time. If the graph or a mathematical description was provided, one would typically integrate the force over the time interval to determine the impulse and use it to calculate the velocity of the block using Newton's second law. To find when the velocity of the block is zero, we would need to know the exact nature of the force variation to calculate when the block changes direction. Unfortunately, without the specific functional form of the force, we cannot solve for (a) the velocity at t = 5 s, or (b) the time at which velocity is zero.