A 3.00 kg block starts from rest at the top of a 30° incline and slides a distan

Question

A 3.00 kg block starts from rest at the top of a 30° incline and slides a distance of 1.80 m down the incline in 1.60 s.

(a) Find the magnitude of the acceleration of the block.

(b) What is the coefficient of kinetic friction between block and plane?


(c) What is the frictional force acting on the block?
Magnitude? ___________________

Is the direction up incline, down incline, normal to incline and upward or normal to incline and downward?

please answer with units, show all work, and clearly state the answer. Thank you!

Explanation / Answer

  (a)

s = vi*t + 0.5*a*t²

1.80 = 0*(1.6) + 0.5*a*(1.6)²

Solving for a:

a = 1.406 m/s² => Answer 1!

(b)

Fx = m*a

W*sin30° - Fk = m*a

3(9.8)sin30° - k*(3)(9.8)cos30° = 3*(1.40)   

Solving for k:

k = 0.41 => Answer 2!

(c)

Fk = k*N

Fk = 0.41*(3)(9.8)cos30°

Fk = 10.43 Newtons =>down incline Answer 3!

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