Question

Carol wants to move her 32kg sofa to a different room in the house. She places "sofa sliders", slippery disks with coefficient of kinetic friction= 0.080, on the carpet, under the feet of the sofa. She then pushes the sofa at a steady 0.40 m/s accross the floor using a force of 25 N. If Carol had pushed the sofa with a force of 30 N, instead of 25N, choose ONLY one correct answer below:                                                             a. the box would move with a faster constant velocity.                                                                        b. the box would move with constant acceleration.                                                                c. the box would move with the same constant velocity.                                                                         d. the box would move with increasing acceleration.

Answer 1

From Newton's Second Law of motion , the net force on a body equals the product of it's mass and the acceleration in the direction of force.In the first case when the sofa is moving with constant velocity, the acceleration is zero. So the applied force and the kinetic frictional force must be equal and opposite. Implies that the kinetic frictional force is F_k = 25 N.

Now in the second case, applied force is F = 30 N, so the net force is F_net = F - F_k = 5 N, so there is some constant net force and so there will be a constant acceleration. so the answer is Option - b) Box will move with constant acceleration.