Question

A student needs to move a large carton of books with a total mass of 120 kg, to get a better view out the window. The coefficient of static friction (μ_s) between the cardboard boxes and the tile floor is 0.42, and the coefficient of kinetic friction (μ_k) is 0.30. With what horizontal force will the student have to push in order to get the stack of books to start moving? Round to the nearest whole number and include units.

Really need help with this problem- thank you in advance!

Answer 1

Mass of the large carton of books = m = 120 kg

Coefficient of static friction = _s = 0.42

Coefficient of kinetic friction = _k = 0.3

Gravitational acceleratioin = g = 9.81 m/s²

Horizontal force applied by the student = F

Friction force on the large carton of books = f

The student will have to overcome the static friction acting on the large carton of books to get the stack moving from rest.

From the free body diagram,

N = mg

f = _sN

f = _smg

F = f

F = _smg

F = (0.42)(120)(9.81)

F = 494.42 N

Rounding off to nearest whole number,

F = 494 N

The student will have to apply a horizontal force of 494 N to get the stack of books to start moving.