A 10 kg block sits on a flat surface whose μs=0.60 and whose μk is 0.40

Question

a. What horizontal force is required to get the block move?

b.If we continue to apply the same force as in part a. what will the blocks acceleration be?

In the answer:
force=.6*mg to move
net force=ma
first force-.6mg=ma solve for a

My question:

what is the first force??... should i subtract it to .6mg?

thanks.

Answer 1

(a) F=F(fr) = μ(s) •N=
= μ(s) •m•g=0.6•10•9.8=58.8 N

(b) ma=F-F1(fr) =
=F- μ(k) •N= F- μ(k) •m•g,
a = (F/m) - μ(k)•g= (58.8/10) – 0.4•9.8 =
=5.88-3.92= 1.96 m/s²