Question

A car travelling at 25 m/s slams its break leaving skids marks along a distance 125 m as it comes to rest. the coefficient f friction between the tire and the road is
a 5
b 2.5
c 1
2 .4
e .25

A 500N worker pulling a 500 N crate on a rope with a force of 50 N at a constant velocity if the coefficient of friction for the worker is 0.05 and the crate is 0.04 what is the acceleration of the worker?
a .001m/s^2
b .1m/s^2
c 1m/s^2
d 2m/s^2
e 5m/s^2
please show work so i can understand how to solve it. ty in advance.

Answer 1

average speed during stop = 25/2 = 12.5 m/s
time to stop, t = 125/12.5 = 10 s

v = Vi + a t
0 = 25 + a(10)
a = -2.5 m/s^2

F = m a
F = -2.5 m

F = -mu m g
F = -mu m (9.81)
so
mu(9.81)=2.5
mu = 2.5/9.81

Answer 2

I do not understand your second problem.