a) A sidewalk is to be constructed around a swimming pool that measures (10.0 ± 0.1) m by (17.0 ± 0.1) m. If the sidewalk is to measure (1.00 ± 0.01) m wide by (9.0 ± 0.1) cm thick, what volume of concrete is needed, and what is the approximate uncertainty of this volume?

b) A child throws vertically a pebble into the air with initial speed vi. Another child drops a ball at the same instant. Compare the accelerations of the two objects while they are in flight.

c) Is it possible for the velocity and the acceleration of an object to have opposite signs? If not, state a proof. If so, give an example of such a situation and sketch a velocity vs. time graph to prove your point.