A crate of weight W is being pushed across a horizontal surface by a force directed at an angle of 20° below the horizontal.What is the magnitude of the normal force on the crate?
A) It is less than W.
B) It equals W.
C) It is more than W.
D) None of the above since the coefficient of kinetic friction is not given.

Question

Quizplus · Accepted Answer

The force pushing the crate has two components, one perpendicular to the surface and one parallel to the surface. The perpendicular component balances out the normal force, so the magnitude of the normal force is equal to the weight of the crate, which is W. The force pushing the crate also has a horizontal component, which is opposed by friction. However, the magnitude of the normal force is not affected by the coefficient of kinetic friction, so the answer is not affected by the information that the coefficient is not given. Therefore, choice C is the correct answer.

A Crate of Weight W Is Being Pushed Across a Horizontal