# Homework Help: Friction and Banked road question

1. Oct 31, 2008

### msq126

Hello Everybody. I am having a very difficult time with these two questions.

The first question:

The system shown in Figure 4.54 has an acceleration of magnitude 1.77 m/s2, where m1 = 3.90 kg and m2 = 9.40 kg. Assume that the coefficient of kinetic friction between block and incline is the same for both inclines.

Figure 4.54
http://www.webassign.net/serpop/p4-54alt.gif

a)Find the coefficient of kinetic friction.?

b)Find the tension in the string. (N)

The Second Question:

A car rounds a banked curve as in the figure below. The radius of curvature of the road is R, the banking angle is θ, and the coefficient of static friction is μs.

http://www.webassign.net/serpop/5-13.gif

a)Determine the range of speeds the car can have without slipping up or down the banked surface. (Use theta for θ, mu for μs, R and g as necessary.)

vmin =

vmax=

b)Find the minimum value for μs such that the minimum speed is zero. (Use theta for θ, and R and g as necessary.)

μs =

c)What is the range of speeds possible if R = 100 m, θ = 10.0°, and μs = 0.110 (slippery conditions)?

vmin =

vmax=

-----------------------------

I would really appreciate it if someone could help me.

2. Nov 1, 2008

### tiny-tim

Welcome to PF!

Hi msq126! Welcome to PF!

Hint: try good ol' Newton's second law for both questions.

Anyway, show us what you've tried, and where you're stuck, and then we'll know how to help.