Chapter 4, Problem 74GP

* Emily pulls a 5-kg block across a rough horizontal surface, exerting a constant force on the block. The magnitude of the force is initially 5 N, and the block moves at a constant velocity of 2 m/s. While the block is moving, Emily instantly increases the force to 10 N. How will the block move now?

Andrew says: The block will move at a constant velocity of 4 m/s because it was initially moving with constant velocity and the final force is two times larger than the initial force.

Jasit says: The block will move at a constant acceleration of 2 m/s because the sum of the forces exerted on the block is 10 N and the mass of the block is 5 kg.

Mary says: The block will move at a constant acceleration of ${\text{1 m/s}}^{\text{2}}$ because the sum of the forces exerted on the block is 5 N and the mass of the block is 5 kg.