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# F = ma problem Watch

1. Can someone please help me with this question. No matter how many times I try, I keep getting the wrong answer.

Question:
Three boxes in contact are being pushed along a system of rollers. The two outer boxes each have a mass of 140 kg and the middle box has a mass of 80 kg. The single pushing force is 220 N. By drawing suitable free-body force diagrams, calculate,

(a) the acceleration of the boxes

Apparently the answer is 0.61ms^-2

and heres my working out:
220/140 = 1.57ms^-2
220/80 = 2.75ms^-2
2. (Original post by CookieHero)
^
Consider the boxes as a single object with mass (140 + 140 + 80)kg, then try again
3. 140+140+80=360

220/360=0.61ms^-2
4. (Original post by CookieHero)
Can someone please help me with this question. No matter how many times I try, I keep getting the wrong answer.

Question:
Three boxes in contact are being pushed along a system of rollers. The two outer boxes each have a mass of 140 kg and the middle box has a mass of 80 kg. The single pushing force is 220 N. By drawing suitable free-body force diagrams, calculate,

(a) the acceleration of the boxes

Apparently the answer is 0.61ms^-2

and heres my working out:
220/140 = 1.57ms^-2
220/80 = 2.75ms^-2
Total F/ Total m= a
Total F= 220N
Total m= 140 + 140 + 80
220/320 = 0.61m/s^2
5. Thanks for the help guys

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