3 . A —The net force is a constant negative value, and the acceleration must also be constant and
negative. Therefore, the velocity-time graph must have a negative slope. This eliminates choice B.
Choices C and D start with a velocity of zero, yet their position-time graphs both begin with a
positive slope, which is inconsistent. Choice E ends with a zero velocity, yet the position-time graph
ends with a negative slope, which is inconsistent. This leaves choice A as the only viable graph that
matches the force-time graph.
4 . E —All the blocks move as a unit, with the same acceleration of . Since each block has the
same acceleration, the block with the largest mass will require the largest net force acting on it to
maintain the same acceleration.