Forces On An Inclined Plane. F N. Think about the forces as she sleds down the hill in the laundry basket (if it is not a non-frictionless surface). Can you label them? . F f. 30°. What is the formula used to calculate F g ?. F g. = mg. How many other forces are there? (Don’t make any up!).
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Think about the forces as she sleds down the hill in the laundry basket (if it is not a non-frictionless surface). Can you label them?
What is the formula used to calculate Fg?
How many other forces are there? (Don’t make any up!)
Two; the normal force (FN) and the force of friction (Ff).
The force due to gravity can be broken up into vectors using the tip to tail method. They are Fgll and Fg┴.
= Fgsin θ
The formulas used to calculate the components are:
= Fgcos θ
One way to remember when to use cosine or sine is to look at the formulas on your reference table. Ax = A cos θ (horizontal) and Ay = A sin θ (vertical). Just use the opposite function for that direction when on an incline. Fg┴ = Fgcos θ (vertical) and Fgll = Fgsin θ(horizontal).
of the forces in the x- direction)
Example: the tip to tail method. They are F
If a 60 kg person is sledding down a hill on waxed skis (yes, it’s a laundry basket, but just pretend!) at a 30o incline at a constant velocity, calculate Fnet, FN, Fgll, Fg┴ , Fg, and Ff.
The easiest thing to find first is the weight (Fg).
Use the weight to find it’s vectors.
Fg┴ = Fgcos θ
Fgll = Fgsin θ
Fgll = (588.6N)sin(30°)
Fgll = (588.6N)(0.500)
Fgll = 294.3N
Fg┴ = (588.6N)cos(30°)
Fg┴ = (588.6N)(0.866)
Fg┴ = 509.73N
What is the normal force equal to? (Remember, it has to be equal and opposite of another force.)
It is equal to Fg┴. The normal force is pushing down with 509.73N of force while the ground is pushing up with an equal amount of force.
FN = 509.73N
To find the force of friction, plug in the normal force and the coefficient of friction that says waxed ski on snow.
This would be ________ friction because it is SLIDING.
Ff = μFN
*Since coefficients of friction don’t have units, keep the unit of a Newton.*
Ff = (0.05)(509.73N)
Ff = 25.49N
Since she is going down the hill at a constant velocity, what does that mean?
Ff = 25.49N
Keep that in mind!
ΣFx = Fnet = ma = Fgll – Ff
Fnet = Fgll– Ff
Subtract the force of friction because it is in the opposite direction of motion.
Fnet = 294.3N – 25.49N