# Homework Help: Calculating forces

1. Feb 24, 2014

### lola0706

1. The problem statement, all variables and given/known data

two horizontal wire which are separated by 50 degrees are pulling on a 2180 kg mass and cause it to accelerate to the west at 0.25 m/s2. the tension in each rope is 4200.

a) find the net force on the mass
b) how much friction is acting on the mass?

2. Relevant equations

fnet= ma
cos law
sine law

f = fah-fnet

3. The attempt at a solution

so i drew out a free body diagram and calculated the components.
x1 = cos25 (4200) = 3806 N
y1 = sin25 (4200) = 1775 N

x2 = the same as x1
y2 = the same as y1

i found fnet by going mass * acceleration and got 545 N

now calculating friction is difficult. i do not know if i am supposed to use only one x component or both. am i supposed to add 545 or subtract it? all help is appreciated. thanks

Last edited: Feb 24, 2014
2. Feb 24, 2014

### Staff: Mentor

Welcome to the PF.

Is there a figure/diagram that goes with this question? Can you scan it or copy/paste it as an attachment?

3. Feb 24, 2014

### lola0706

this is what i assume the diagram would look like

the 25 degrees would be the 50 degrees shared by the 2 triangle components

oh and thanks for the welcome! :)

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4. Feb 24, 2014

### Staff: Mentor

Let x be the direction in which the mass is moving. What is the component of force exerted by each of the ropes in the x direction? What is the sum of these two components of force? Write a force balance for the mass in the x direction that includes the two components of rope force, the frictional force, and the mass times acceleration.

Chet