Rubber stopper hanging from the view view mirror of a car

[shawli]

Homework Statement

A 18g rubber stopper is suspended by a 45-cm string from the rear view mirror of a car. As the car accelerates eastward, the string makes an angle of 5.1 degrees with the vertical. Determine the acceleration of the car.

Homework Equations

The Attempt at a Solution

I'm totally stumped. There are no forces or anything given, not even sure what the diagram should look like : |. Help !

 

[Doc Al]

What forces act on the stopper?

 

[shawli]

Gravity?
And it's positioned at an angle because of inertia ? I don't think that can be drawn out as a force though.

 

[Doc Al]

Yes, gravity is one of the two forces acting on the stopper. What's the other? (What's attached to the stopper?)

 

[shawli]

Oh right, tension !

So, from the rubber stopper, a force point outward diagonally (along the string) is the force of tension.
And a force pointing directly downwards is gravity?

 

[Doc Al]

So, from the rubber stopper, a force point outward diagonally (along the string) is the force of tension.
And a force pointing directly downwards is gravity?

Exactly!

 

[shawli]

Oh okay! One more thing --the length of the string is given. I get confused when questions about the magnitude of forces give me the length or distance of something. I'm not sure what I can do with that?

 

[Doc Al]

Just analyze the forces as you normally would. Ignore any extraneous information given.