Physics question. Using Free Body Diagrams

Question

A 3.00 kg block starts from rest at the top of a 28.0° incline and slides 2.00 m down the incline in 1.45 s.

(a) Find the acceleration of the block.

(b) Find the coefficient of kinetic friction between the block and the incline.

(c) Find the frictional force acting on the block.

(d) Find the speed of the block after it has slid 2.00 m.

 

Answer 1

a) Using big five,

d = (1/2)a t²

Plug in given data,

2 = (1/2)a (1.45)² 

a = 1.90 m/s²

b) Draw free body diagram, and apply Newton's second law in the direction parallel to the inclined face,

mgsin28^o - mgμcos28^o = ma

μ = (gsin28^o - a)/(gcos28^o) = .312

c) F_f = mgμcos28^o = 8.10 N
d) v = at = 2.76 m/s

or

v² = 2ad

v = √(2ad) = 2.76 m/s