Space Time & Motion A.2 Forces & Momentum (id: 318c73191)

本题目来源于试卷: Space Time & Motion A.2 Forces & Momentum，类别为 IB物理学

[单选题]
Two bodies of masses 2 kg and 3 kg are connected by a thread and pulled in the upward direction with an acceleration of g due to an upward force F
The thread between the masses is cut. Which of the following is correct for the bodies just after the cut?
What is Acceleration of 3 kg mass and what is Acceleration of 2kg mass

A. g;g
B. 4g;g
C. 4g;4g
D. g;4g


参考答案:  D


本题详细解析:

$\underline{\text{Explanation}}$: 
$F=ma$

Before the thread is cut,
$F-W=ma$ for the system 
$W=mg=5g$ and  $ma=5g$
Therefore $F=5g+5g=10g$

Just after the cut, the 3kg mass is only under the influence of gravity, so its accleration is equal to $g$

The net force on the 2 kg mass is F - 2g = 10g - 2g = 8g

Acceleration of the 3 kg mass = $g$

Acceleration of 2 kg mass = ${\displaystyle \frac{8g}{2}}=4g$

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