# can anyone help me please ? physics problem ?

### 3 Answers

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- oldschoolLv 72 months ago
The weight of the 12kg block on the 9kg block = 12*9.8 = 117.6N

The friction force opposing motion = 117.6*0.3 = 35.28N

Fnet = 5*9.8 - 35.28 = 13.72N

a = Fnet/(9+5) = 0.98m/s² <<<<<

OR we can use the tension T:

(5*9.8 - T)/5kg = a = (T - 12*9.8*0.3)/9kg

Cross multiply

9(5*9.8 - T) = 5(T - 12*9.8*0.3)

441 - 9T = 5T - 176.4

441+176.4 = 617.4 = 14T

T = 44.1

a = (49 - 44.1)/5 = 0.98m/s² same answer.

a = (44.1 - 12*9.8*0.3)/9kg = 0.98m/s²

That rounds to 1m/s² the first choice.

- billrussell42Lv 72 months ago
weight of 12 kg block is 12•9.8 N

force of friction is 0.3•12•9.8 = 4•9.8 N

force due to weight is 5•9.8 N

net force is the difference, 1•9.8 N

a = F/m = 9.8 / (5+9) = 0.7 m/s²

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