A refrigerator weighs 2000 N and rests on a flat floor A wor

A refrigerator weighs 2000 N and rests on a flat floor. A worker pushes horizontally on the refrigerator with a force of magnitude 25 N to set the refrigerator in motion, and then he pushes with a force of magnitude 20 N to keep it moving. What force or forces does the refrigerator apply to the worker? A pushing force of 25 N both before and after the refrigerator began moving A pushing force of 25 N at first, and then a pushing force of 20 N A pushing force of 2000 N both before and after the refrigerator began moving A pushing force of 20 N both before and after the refrigerator began moving

Solution

Option B.

Initially, the object is at rest. So in order to start its motion, we need to overcome static friction which is 25N.

Once it is set to be in motion, the friction which new opposes force is Dynamic friction - which is less than static friction. Now, since only 20N is required to keep it moving, the dynamic friction will be 20N.

So, 25N at the starting and than 20N.