ITT Technical Institute

Framingham, Massachusetts

Quarter 6 Electronics Physics

Instructor: Paul BurneyName __________________________________

Friction (Test #5)

Instructions:Please solve the following problems. Credit will be given for work completed so make sure to show it! Some helpful information can be found below.

Force Formulas

Friction FormulasF = ma

F

_{g}= mgF

_{down a ramp}= mg sin qN

_{flat surface}= mgN

_{on a ramp}= mg cos qf

_{s}= m_{s}Nf

_{k}= m_{k}Nm

_{s}= tan q_{s}m

_{k}= tan q_{k}

1) A graduate student in physics, working part-time with a moving company, figures out that the coefficients of static and kinetic friction between a 100 kg box and the floor are 0.96 and 0.82 respectively.

a) How much force is needed to start the box moving?

b) How much force is needed to continue moving the box once it is in motion?

2) A car is to be placed on a metal incline for display. If only friction is to be used to keep the car on the incline, what is the maximum angle at which the car can be inclined?

m_{s}= 0.80 and m_{k}= 0.60.

3) A 1350 kg car narrowly avoids running off of a washed out bridge. The coefficient of friction between the car and the road is 0.55. If the skid marks are 100 meters long, what was the initial velocity of the car?