Help Solve Skier Problem Homework

[peyton]

Homework Statement

if a skier goes down a hill that is 20m high and 70 m long perpendicular to the height... and she weighs 50kg and her intial veloctiy is 5 m/s. how fast is she going at the bottom if the force of gravity up the hill is 40N??
I just don't get it!
PLease help me

Homework Equations

total energy= kinetic energy + gravitational energy

work = Fd

The Attempt at a Solution

Et= .5x50x(5x5)+ 50 x 9.8 x20
= 10425

and i don't know where to go from here please help me!
i have a test tomorrow and i don't understand

 

[tiny-tim]

Welcome to PF!

Hi peyton! Welcome to PF!

Homework Statement [/b]
if a skier goes down a hill that is 20m high and 70 m long perpendicular to the height... and she weighs 50kg and her intial veloctiy is 5 m/s. how fast is she going at the bottom if the force of gravity up the hill is 40N??
I just don't get it!

What a terrible question …

how can gravity be up the hill … doesn't your professor know what "up" means??

and how can anyone have a weight in kg? weight is in Newtons, mass is in kg

hmm … if her mass is 50kg, the force of gravity down the hill would be about 140 N, not 40 N (it isn't, is it?) …

i've no idea what this question means …

if you have to answer it, I suggest you ignore the 40 N, which is indeed what you've already done …

Et= .5x50x(5x5)+ 50 x 9.8 x20
= 10425

… now what speed does that correspond to?

total energy= kinetic energy + gravitational energy

"total energy" isn't really a helpful concept (and nobody calls it "Et" ) …

I suggest you say KE + PE = constant, or ∆(KE) = -∆(PE)

 

[peyton]

btw i am Canadian
the 10425J
and it was the force of friction was 40N up hill

i need to find the velocity at the bottom of the hill

 

[tiny-tim]

and it was the force of friction was 40N up hill

D'oh!

In that case, you need to find the work done by the friction force, and use the work-energy theorem.

btw i am Canadian

ahh!

 

[peyton]

then what ?
find the difference then use that force to find the velocity at the bottom of the slope