Student Pulling Box Homework: Find Acceleration

[sprinter08]

Homework Statement

The student in item 1 (in parenthesis below) moves the box up a ramp inclined at 12 degrees with the horizontal. If the box starts from rest at the bottom of the ramp and is pulled at an angle of 25 degrees with respect to the incline and with the same 185N force, what is the acceleration up the ramp. Assume the mu is 0.27.

(A student pulls on a rope attached to a box of books and moves the box down the hall. The student pulls with a force of 185N at an angle of 25 degrees above horizontal. The box has a mass of 35 kg and mu between the box and the floor is 0.27. Find the acceleration.)

Homework Equations

The Attempt at a Solution

Would the answer be 2.9 m/s^2?

 

[BigJDubs]

I used the equation Fnet = ma and did 185(sin25)cos12 to get the net force. I then divided that by the mass to get the acceleration.

 

[Moetasim]

Hello, based on the given information, the acceleration up the ramp can be calculated using the formula a = (Fsinθ - μmgcosθ)/m, where F is the applied force, θ is the angle at which the force is applied, μ is the coefficient of friction, m is the mass of the box, and g is the acceleration due to gravity. Plugging in the given values, we get:

a = [(185N)(sin25°) - (0.27)(35kg)(9.8m/s^2)(cos12°)]/35kg

a = 2.9 m/s^2

Therefore, your answer of 2.9 m/s^2 is correct. Keep in mind that the acceleration is directed up the ramp, as the box is being pulled up the ramp. I hope this helps!