Answer:
The magnitude of Keith’s push is 230 N
Step-by-step explanation:
Given:
Mass of chuck,
kg
Acceleration of the chuck,
m/s².
Coefficient of friction,

Frictional force acts to left as motion is to right.
Frictional force is given as:

as net force in vertical direction is zero.
Total force to the right,

Total force to the left,

Net force acting on the chuck,

According to Newton's second law,

Keith applies a force of
towards left.
Therefore, the magnitude of Keith’s push is 230 N.