What force is needed to keeps 20kg box moving at a constant velocity when the mk is 0.3021 and the force is a pull at 20 degree to the ground

63.0 N

Explanation:

We need to consider the resultant of the forces acting along the surface. We have two forces:

- The component of the pull parallel to the ground, which is given by

where is the angle between the force and the ground

- The frictional force, given by

where is the coefficient of friction, m = 20 kg is the mass of the box and g=9.8 m/s^2.

The box is moving at constant velocity, this means zero acceleration, so the equation of equilibrium becomes:

From which we can find the magnitude of the pull, F:

iron would move it is magnetic there is a mag field around the current in the wire