# Find the magnitudes of all of the forces acting on the sled

1. Apr 7, 2015

### NkaujHelp

1. The problem statement, all variables and given/known data
A person pulls on a rope attached to a 5 kg sled. The rope makes an angle of 30 degrees with the horizontal. Sled accelerates horizontally at 1.7 m/s^2. There is no friction.

2. Relevant equations
ma = Fnet
mg = Fgravity

3. The attempt at a solution
Fnorm = earth force up on sled
Fr = the force of the rope of the sled being pulled

The x and y components for Fr would be y = Frsinθ and x=Frcosθ.
Vector of Fnorm = <0, Fnorm>
Vector of Fg = <0, -50>
Vector of Fr = <Frcos30, Frsin30>

Fnetx => 8.5 = Frcos30
Fnety => 0 = Fc - 50 + Frsin30

So I got this far and starting doing algebraic stuff to solve for Fr and then plugging that into the second equation. From there, I solved for Fc, and the value was 45.095 N. And from the Fnetx equation, Fr = 9.8 N.
However, when I added all the magnitudes of forces, my answer does not equal to the Fnet, which is ma = 8.5 N.
Can someone help me with this? Have I forgotten something? Am I even doing this right?

2. Apr 7, 2015

### Staff: Mentor

Show us how you added up the forces to get the net force. Your answers so far look OK.

Chet

3. Apr 7, 2015

### NkaujHelp

For the net force, I did the force magnitude of Fnorm plus force magnitude of Fr minus the force magnitude of Fg, which is 8.5 N + 45.095 N - 50 N. That answer got me 3.595 N.

4. Apr 7, 2015

### Staff: Mentor

The forces have to be added as vectors, not as scalars.

Chet

5. Apr 7, 2015

### NkaujHelp

How do I do that?

6. Apr 7, 2015

### Staff: Mentor

You do it by adding their components. But, you've already done that.

Chet