Find the acceleration of the books:

Question

A Student moves a box of books with a rope by pulling the rope with a force of 90 N at an angle of 30°.

 

The books have a mass of 20 kg and a coefficient of friction between the box and floor is .50. Find the acceleration of the books.

Answer 1

I assume the 30° angle is above the horizontal.  You need to state that in the problem.

 

F = net force

T = tension in rope = 90 N

μ = 0.50

m = mass of books = 20 kg

θ = 30º

 

Newton's 2nd law:

 

F = ma

F = Tcosθ - μmg

 

⇒

 

ma = Tcosθ - μmg

 

a = (Tcosθ - μmg)/m

 

You know T, θ, μ, g, and m.  Now just plug in the numbers and you will have your answer.