Question

a) When rebuilding her car's engine, a physics major must exert 445 N of force to insert a dry steel piston into a steel cylinder. What is the magnitude if the normal force in newtons between the piston and cyliner?

b) What is the magnitude of the force in newtons she would have to exert if the steel parts were oiled?

Answer 1

a) The student applies a force of 445 N to insert the piston into the cylinder. This force must be equal or greater than the frictional force to succesfully einsert the piston into the cylinder.

For a normal force N, frictional force is given by

is the coefficient of friction which here for dry steel is about 0.7

Putting the values,

b) Using standard tables coefficient of friction of oiled steel is about 0.05

Putting the values, the force the student must apply is