# Need help finding degrees to the right of the forward direct

1. Oct 13, 2015

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

Two forces are applied to a car in an effort to move it, as shown in the figure below. (Let
F1 = 430 N (10 degrees)
and
F2 = 356 N. (30 degrees)
Assume up and to the right are in the positive directions.)
(a) What is the resultant vector of these two forces?
magnitude=?
° to the right of the forward direction=?
(b)If the car has a mass of 3,000 kg, what acceleration does it have? Ignore friction.
2. Relevant equations
(430sin(10)) + 356sin(30)=252.67x
(430cos(10)) + 356cos(30)=731.78y
a=(731.78)/(3000)

F=ma
angle = tan-1((731.78y)/(252.67x)) ??

3. The attempt at a solution
For part a I got 774.17N for the magnitude and it was correct
For part b I got 0.244 for the acceleration and it was correct
But I can not for the life of me solve for angle to the right of the forward direction

#### Attached Files:

• ###### physiccar.PNG
File size:
9.5 KB
Views:
58
2. Oct 13, 2015

### SteamKing

Staff Emeritus
This calculation is incorrect. If you look at the diagram, the x-components of each force act in opposite directions, so you can't simply add them together to find the resultant force in the x-direction.

Always indicate units with your calculations.

These calculations are OK.

If you are still having trouble, make a small sketch of the resultant force vector and F1 and F2. You should be able to find the correct angle once you have calculated the correct x-component of the resultant force.

3. Oct 13, 2015

When I recalculated my x-component of the resultant force I got 103.33 N and an angle of 81.96 degrees.
F2x-F1x= Resultant x-component
(356 N sin(30)) - (430 N sin(10))= 103.33 N
tan-1=((731.78)/(103.33)) = 81.96
would 81.96 be the degrees to the right of the forward direction then that the question is asking for?
Thanks for the clarification and help!

4. Oct 13, 2015

### SteamKing

Staff Emeritus
Did you draw the resultant and F1 and F2 to see if this calculation is correct?

I think you have calculated the wrong angle.

Does it seem reasonable that the resultant of F1 and F2 would act at almost a right angle to them?