Cyclist coasting down a hill cons. of energy

  • Thread starter Thread starter totallyclone
  • Start date Start date
  • Tags Tags
    Energy Hill
AI Thread Summary
A bicyclist coasts down a 7.0° hill at a steady speed of 5.0 m/s, with a total mass of 75 kg. To determine the power output required to climb the hill at the same speed, the cyclist's energy considerations include kinetic and gravitational potential energy. The calculations suggest that friction must be accounted for, as coasting at a constant speed implies opposing forces are present. The final power output calculated was 448W, but the presence of friction needs to be factored into the overall analysis. Understanding these forces is crucial for accurately determining the cyclist's power requirements.
totallyclone
Messages
54
Reaction score
0

Homework Statement


A bicyclist coasts down a 7.0° hill at a steady speed of 5.0m/s. Assuming a total mass of 75kg (bicycle plus rider), what must be the cyclist's power output to climb the same hill at the same speed?


Homework Equations


EK=1/2 mv2
EG=mgh
P=W/T


The Attempt at a Solution


I tried the question and this is what I got but I'm answer if this is right... not sure if there's a Force of friction though because I read the question and assumed there isn't any force of friction... but I'm unsure... :rolleyes:

P=W/T
P=-WGΔdcos180°/T
P=-WGvcos180°
P=-mgsin7.0°(5.0)cos180°
P=-(75)(9.8)sin7.0°(5.0)cos180°
P=448W
 
Physics news on Phys.org
Well if the cyclist goes down the hill with constant speed, then there must be some kind of force that's stopping him from accelerating, so you should account for it accordingly.
 
hi totallyclone! :smile:
totallyclone said:
A bicyclist coasts down a 7.0° hill at a steady speed of 5.0m/s. Assuming a total mass of 75kg (bicycle plus rider), what must be the cyclist's power output to climb the same hill at the same speed?
…
not sure if there's a Force of friction …

he couldn't coast (at a steady speed) if there wasn't friction, could he? :wink:
 
tiny-tim said:
hi totallyclone! :smile:


he couldn't coast (at a steady speed) if there wasn't friction, could he? :wink:

so...THERE'S FRICTION!?
 
yup! :smile:
 

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
View full post »
Thread 'A cylinder connected to a hanging mass'

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
View full post »

Similar threads

Find mechanical energy lost when a cyclist goes down a hill
Replies
3
Views
2K
What velocity does a train need to go up and down the hill
Replies
37
Views
4K
Calculating Power Output for a Cyclist Coasting Down a 7.2 Degree Hill
Replies
1
Views
4K
Bicyclist coasting down hill (Newton's Laws)
Replies
4
Views
7K
Sledding Down a Hill: Calculating Friction and Velocity
Replies
31
Views
3K
How high can it coast up the hill, if you neglect friction?
Replies
1
Views
4K
How Long Does It Take a Car to Climb a Hill with Limited Power?
Replies
2
Views
5K
Calculating Power Output to Climb a 7.0 Degree Hill
Replies
7
Views
10K
What Is the Cyclist's Power Output to Climb a 7.0 Degree Hill at 5.0 m/s?
Replies
6
Views
28K
What is the deceleration of a snowboarder going up a 5.0° slope?
Replies
2
Views
13K

Hot Threads

Recent Insights

Back
Top