Friction Force Calculation: 1500 kg Car on 4 Degree Incline

[julestux]

homework question, please help! :)

Homework Statement

A 1500 kg car is parked on a 4 degree incline. The acceleration of gravity is 9.8 meters per second squared. Find the force of friction keeping the car from sliding down the incline. Answer in units of Newtons.

Homework Equations

What formula(s) would you use?

The Attempt at a Solution

 

[jedishrfu]

one draw a force diagram and then use trig to break up the force of gravity into two components:
- parallel to the incline
- perpendicular to the incline

Your frictional force needs to counteract one of those components. which one?

 

[tiny-tim]

welcome to pf!

Homework Statement

A 1500 kg car is parked on a 4 degree incline. The acceleration of gravity is 9.8 meters per second squared. Find the force of friction keeping the car from sliding down the incline. Answer in units of Newtons.

Homework Equations

What formula(s) would you use?

The Attempt at a Solution

hi julestux! welcome to pf!

first, find the normal force …

show us what you get ​

 

[julestux]

the normal force I got was 14664.19

 

[Dick]

the normal force I got was 14664.19

That's good. But I think you actually want the tangential force. That's what friction has to offset. And do specify units on a force.

 

[tiny-tim]

the normal force I got was 14664.19

(i haven't checked your result)

ok, now take components (of all the forces) along the slope …

they have to add to zero ​

 

[julestux]

how do they add up to zero?

 

[cepheid]

how do they add up to zero?

What do you mean by "how?" Add them up and set the sum equal to zero. It's a necessary condition if the object is stationary, and therefore unaccelerating.

 

[tiny-tim]

yes

julestux, are you confused by assuming static friction = µN ?

it isn't, it's ≤ µN, you find out how much it is by summing the components to zero

anyway, show us what you get for the compontents along the slope ​