Physics HW Force Question, blocks with masses

Question

Blocks with masses of 1.0 kg, 2.0 kg, and 3.0 kg are lined up in a row on a frictionless table. All three are pushed forward by a 13 N force applied to the 1.0 kg block.

-How much force does the 2.0 kg block exert on the 3.0 kg block?

-How much force does the 2.0 kg block exert on the 1.0 kg block?

Answer 1

All blocks would move at same acceleration

a=Pulling force/(total mass of the blocks)=13N/(1kg+2kg+3kg)=13N/6kg=2.2m/s²

The force applied from the block2 to the block 3 would be the force needed to give the block 3 the acceleration a:

F_3<=2=3kg x 2.2m/s²=6.6N

By 3rfNewtonian Law, the block 2 would pull on the block 1 with a force equal and oppositely directed to the force with which block1 would pull on block2 (which must be equal to (m₂+m₃)a= 5kg x 2.2m/s²=11N

Note: in the problem sig.figs requirements were not stated.

(If a standard sig.fig. policy is to be followed, only 1 sig. fig. must have been retained in all answers)