Missed my class and don't know how to even begin.

In summary, a 100kg bicycle and rider travel uphill at 16 m/s, with the rider slamming on the brakes and skidding to a stop. The coefficient of friction is given as (0.8, 0.7). The problem involves finding the distance skidded and elapsed time before the bike stops. The equations for this problem are v2-u2 =2as and v=u+at. The forces acting on the bike are friction and gravity, with the acceleration found from the friction equation. The final solution for distance and time may be affected by other factors.
  • #1
Dko
9
0

Homework Statement



a 100kg bicycle and rider initially move at 16 m/s up a 15 degree hill. The rider slams on the brakes and skids to rest. The coefficient of friction is (0.8, 0.7)

Homework Equations


I have a few but nothing to do with a coefficient of friction.
The last ones given to me where like
MVi + ƩF(Δt) = MVf

The Attempt at a Solution


I can' make any since I was sick for class. I'm sure the professor was supposed to give at least a hand out with some explanation. So could someone at least give me a idea what I have to look up online that will help me get started on this problem?
 
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  • #2
What exactly are you trying to solve for? I'm guessing time?
 
  • #3
Gehh sorry. Why do I keep forgetting that?
a. How far does the bike skid?
b. What was the elapsed time before the bike stops skidding?
 
  • #4
This is what I have to help so far.

(100kg)(16m/s) + ƩF(Δt) = 0

ƩF = (-mg sin(15) + uFn)
→ƩF = (-9.8 x 100kg x sin(15)) + u( 100 x 9.8 x cos 15)

→ƩF = -1232.877407

(100kg)(16m/s) + (-1232.877407)(Δt) = 0

1600 = (1232.877407)(Δt)

Δt = 2.59

I'm not sure if it is right, I might have forgotten a few things. Mainly...how to find ƩF

Please correct me! I'm only a freshman.
 
Last edited:
  • #5
Hi,
The basics are, 2 forces act on the bike:-
Friction=Normal force * coefficient of KINETIC friction = (mg cosθ)*k
gravitational force=mg sinθ

From this info, find acceleration

use v2-u2 =2as to find distance
use v=u+at to find time.

I'm not sure there are no other factors. Pls check!
 

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