A car starts rolling down a l-in-4 hill (l-in-4 means that for each 4 m traveled along the road, the elevation change is 1 m). How fast is it going when it reaches the bottom after traveling 55 m? (a) Ignore friction, (b) Assume an effective coefficient of friction equal to 0.10.

Question

and also

Two boxes, mx — 1.0 kg with a coefficient of kinetic fric tion of 0.10, and m2 = 2.0 kg with a coefficient of 0.20, are placed on a plane inclined at 9 = 30°. (a) What acceleration does each box experience? (b) If a taut string is connected to the boxes (Fig. 4-64), with m2 initially farther down the slope, what is the acceleration of each box? (c) If the initial configuration is reversed with m\ starting lower with a taut string, what is the acceleration of each box?

Answer 1

first:

the normal component of weight is mg*sqrt(15/16)
friction then is mg*sqrt(15/16)*mu

So going 55m, work is mg*sqrt(15/16)*.1*55

final KE=initialPE-workdone.

second question

I dontknow the incline.

Answer 2

the incline is 30 degrees