Bob is pushing a box across the floor at a constant speed of 1.2 m/s, applying a horizontal force whose magnitude is 75 N. Alice is pushing an identical box across the floor at a constant speed of 2.4 m/s, applying a horizontal force.

What is the magnitude of the force that Alice is applying to the box?
F = N

75 N

Explanation:

Given

Bob is pushing the box with a force of 75 N with constant speed. Constant speed indicates that net force on the block is zero i.e. friction force is balancing the applied force.

so friction force f=75 N

If Alice is pushing an identical box with constant speed so net force acting on box must be equal to an applied force.

As the friction force is 75 N so Alice must be applying a force of 75 N  

answer: 31, 5556. 952 seconds