Posted by Tom on Tuesday, January 31, 2012 at 12:45pm.
I just wanted to be sure if I got the answer right
1. Jenny (75 kg) goes on a ski trip. She goes down a slope that's inclined at 15*. Her drag coefficient is 0.300, the area of contact with the air is 0.750 m^2 and the air density is 1,31 kg/m^3. The coefficient of kinetic friction between the skis and the snow is of 0,185.
Jennys speed according to her distance:
from 0 to 15m/s: between 0m and 50m
from 15 to 20 m/s: between 50m and 100m
constant 20m/s: 100m to 450m
from 20m/s to 0: 450m to 500m
a) What is the Work done by the force of air resistance?
A) I answered 0.687 J which seems very unlikely. This is how I proceeded:
I have the Force of air resistance formula:
I have all of the numbers except for the velocity. So I just used the graph to calculate the total time it took Jenny to complete the slope. It gave me: 37.83 seconds. I then proceeded to divide the total length of the slope which is 500m. by 37.83s. to get her average velocity for that descent. It gave me 13.28 m/s which I then used in the air resistance formula and got 26N of air resistance against her. Then I just went with
W = J/s ---> W = 26 N / 37.83 s.
and it gave me 0.687 J.
Could this possibly be the answer or did I do something wrong?
- Physics - Tom, Tuesday, January 31, 2012 at 6:00pm
so I was supposed to do Fres. X distance
for 1 J = 1N*m. I had mixed the previous formulas up, I had the W for watts instead of Work. So my final answer for the work of the air resistance is actually 26N*500m = 13,000 J or 13 kJ.
is that correct?
- Physics - Tom, Tuesday, January 31, 2012 at 6:02pm
For finding Power, that's where I'll use 13kJ / 37,83 sec. right? = 343.64 watts.
Answer this Question
More Related Questions
- TOm - Hello, this is the last question that I can't seem to or be able to solve...
- Physics - Wrote the name and subject bad in the other post, sry:: Hello, this is...
- PHYSICS!!!!...PLEASE HELP - Ski boots are usually made with releasable bindings...
- Physics :(( help please TT - Ski boots are usually made with releasable ...
- Physics - On a recent ski trup to Vermont, Mr Backman wanted to beat Mr S's ski ...
- algebra - how would I graph the following slope -2: y-intercept: (0, 4) Start at...
- geometry - if sarah gets enough money to go to a movie, jenny will go. if jenny ...
- Math - A ski resort is installing tows on its new ski runs. The baby hill has a ...
- Logic - Lucy goes to stanford. Ben goes to Yale. Eliza goes to Oxford. And Peter...
- Finance - 31. Suppose the market portfolio is equally likely to increase by 30% ...