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Using a horizontal force F, a table is moved across the floor at a constant velocity. How much is the frictional force exerted by the floor on the table?
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Since the table moves at constant velocity , its acceleration is zero, so the net force is zero. The frictional force must balance the applied force exactly.
Therefore the frictional force = F (equal to the applied force, but opposite in direction).
What the motion tells us
What follows
The table moves at a
constant velocity
So its acceleration is
zero
Zero acceleration ⇒
net force = 0
The two horizontal forces must cancel
Applied force =
F
(forward)
Frictional force =
F
(backward)
