There are 10 identical blocks lined up in a row. Each block has a mass of 240 g.

Question

There are 10 identical blocks lined up in a row. Each block has a mass of 240 g. A force

F = 4.00 N

is applied to block 1, as shown in the picture. The coefficient of kinetic friction between each block and the horizontal surface is 0.160. At the instant shown in the picture, the blocks are sliding to the left at a speed of 2.20 m/s. Use

g = 10 N/kg

for this problem.

(a) Calculate the magnitude of the net force acting on block 6.

So I am actually crying about this question because that's how frustrated I am by it. I've tried it 16 times and posted it 3 times on Chegg and everyone keeps giving me the wrong answer. When you do this PLEASE USE G = 10 N ,NOT G = 9.81 N. 9.81 N WILL NOT GET YOU THE RIGHT ANSWER. The answer is not 1.74, 0.004, 0.016, 0.16, or 0.154

Explanation / Answer

lets seprate the systems to study the problem in a simpler form

consider block 1 to 5 as a single mass of 0.24*5=1.2 kg

let this be named as Ml (left mass)

similarly consider block 7 to 10 as a single mass with mass=0.24*4=0.96 kg

let this be named as MR. (right mass)

then as the system is travelling with uniform speed, net force on the system =0

let force applied by block 6 on block Ml is Fl.

this force will be applied to the left.

as the blocks are moving to the left, friction will act towards right

friction force=0.16*1.2*10=1.92 N

writing force balance equation:

F+1.92=Fl

==>Fl=5.92 N

[ remember, this same exact force but in opposite direction (i.e. to the right will be applied on

block 6 as per newton's third law of motion ]

now, for the right block,

let force exerted by block 6 on right block is Fr.

then this force will be towards left to oppose the friction force which is acting to the right.

then Fr=0.16*0.96*10=1.536 N

so net force acting on the block 6=Fl-Fr+friction force, to the right

(Fl is acting to the right, Fr is acting to the left, friction is acting to the right)

net force=4.768 N , to the right direction

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