How Far Will a Car Slide Uphill vs Downhill When Braking?

[domagoj412]

Homework Statement

Car is driving up the hill with speed of 60 km/h. Angle of incline is 17°. Seeing barrier on the road, the driver suddenly stops (breaks the wheels) and starts to slide. If koef. of fiction is [tex]\mu[/tex]=0.6 what is the distance between breaking point and the point when cars stops. Solve the problem with the same parameters when the car is driving down the hill.

(I hope you understand the question, it is a little difficult for me to translate it...)

Homework Equations

Again, I solve it but I'm not sure if is correct..

The Attempt at a Solution

Uphill:
Ek = Ep + Fk*s
1/2 mv^2 = mgh + [tex]\mu[/tex]*m*g*cos([tex]\alpha[/tex])*s
(h = s * sin([tex]\alpha[/tex]))
...
s = 32,7 m

Downhill:
Ek + Ep = Fk*s

 

[vij]

Homework Statement

Car is driving up the hill with speed of 60 km/h. Angle of incline is 17°. Seeing barrier on the road, the driver suddenly stops (breaks the wheels) and starts to slide. If koef. of fiction is [tex]\mu[/tex]=0.6 what is the distance between breaking point and the point when cars stops. Solve the problem with the same parameters when the car is driving down the hill.

(I hope you understand the question, it is a little difficult for me to translate it...)

Homework Equations

Again, I solve it but I'm not sure if is correct..

The Attempt at a Solution

Uphill:
Ek = Ep + Fk*s
1/2 mv^2 = mgh + [tex]\mu[/tex]*m*g*cos([tex]\alpha[/tex])*s
(h = s * sin([tex]\alpha[/tex]))
...
s = 32,7 m

Downhill:
Ek + Ep = Fk*s

Your equations are correct. But the calculation appears to be incorrect. Probably you have not converted km/h into m/s. Try once again and finish both calculations.

 

[domagoj412]

Yes, I got the different result:

16.34 m for uphill and 50.31 m for downhill.

 

[vij]

Yes, I got the different result:

16.34 m for uphill and 50.31 m for downhill.

Your answer is correct now.