# Some help please on a Question

1. Sep 13, 2007

### physics kid

1. The problem statement, all variables and given/known data
This has had me puzzled for a few hours now,
Its about forces acting down a plane.

Q. A car of a mass (m) is travelling with a constant velocity up a hill at an angle (any angle - theta ) to the horizontal as indicated

If F is the resultant force acting on the car, the effective engine force needed to maintain this consant velocity must be
A = mgcos(theta) + F
B = mgcos(theta) - F
C = mgsin(theta) + F
D = mgsin(theta) - F
E = mg + Fsin(theta)

Any help will be apprieciated

My work

I tried making up values for the equations. It worked but it didnt really match the equations matched in the answer.
Fh = fcos(theta) Horizontal Force
Fv = fsin(theta) Vertical Force

As its horizontal I have igonred the answers with sin. But I somehow dont know why it either has to be plus or minus F. Would that not equal an unbalanced force.

Last edited: Sep 13, 2007
2. Sep 13, 2007

### Staff: Mentor

What is the meaning of "Resultant Force"? Resultant of what? (It can't mean net force, since the car is moving at constant velocity.)

3. Sep 13, 2007

### physics kid

the result of all the friction acting on it

Basically just the friction

4. Sep 13, 2007

### learningphysics

what is the net force acting on the car (not the resultant force, but the net force)?

5. Sep 13, 2007

### physics kid

Net force ?

The question dosnt give any values. Its to try and find the correct formula that would work.
All the info Im given is shown there

6. Sep 13, 2007

### learningphysics

hint: the car is moving at a constant velocity... this information should let you know what the net force acting on the car is.