Astudent wants to determine the coefficients of static friction and kinetic friction between a box and a plank. she places the box on the plank and gradually raises one end of the plank. when the angle of inclination with the horizontal reaches 30o , the box starts to slip and slides 2.5 m down the plank in 4.0 s. calculate the coefficients of friction.

the coefficients of static friction is 0.577

the coefficients of fkinetic friction is 0.54

Step-by-step explanation:

given information

θ = 30°

S = 2.5 m

t = 4 s

- Static friction

F - F(friction) = 0

W sin θ = μs W cos θ  

μs = sin θ/ cosθ

   = tan θ

   = tan 30°

   = 0.577

- kinetic friction

S = +

= 0

S =

a = =

  = 0.3

F - F(friction) = m a

W sin θ - μ W cos θ  = m a

mg sin θ - μk mg cos θ  = m a

g sin θ - μk g cos θ  = a

μk = g sin θ  - a / g cos θ

    = 9.8 sin 30° - 0.3 / 9.8 cos 30°

    = 0.54

d

gimmee one of those gold crowns!

~coco

d. 24+-0.114

step-by-step explanation:

the question requires us to calculate the approximate 95% confidence interval for the mean number of ounces of ketchup per bottle in the sample given the following statistics;

sample mean = 24

standard deviation, σ = 0.4

sample size , n = 49

the confidence interval for a population mean is calculated using the formula;

sample mean ± z-score*(σ/sqrt(n))

the z-score associated with a 95% confidence interval, from the standard normal tables, is;

1.96

substituting these values into the formula;

24 ± 1.96*(0.4/7)

= 24 ± 0.112

from the alternatives given, choice d is closest to the above expression;