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Question 17
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A body of mass 3kg resting on a smooth surface is acted upon by forces P(10N, 045o), Q(12N, 180o), R(15N, 215o) and S(8N, 090o). Calculate, correct to one decimal place, the
- resultant force acting in the body.
- acceleration with which the body begins to move
- time it takes to cover the first 4 meters.
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This question was also reported to be poorly attempted by the candidates. Majority of the candidates dodged the question and the few who attempted it could not resolve the forces correctly. Some of them also had problems representing the forces in a diagram.
Resultant R =  +  +  +  = 
/R/ =  = 18.4N to one decimal place.
To obtain the acceleration, the formular F = ma is used. Here, F = 18.4N,
m = 3kg. Therefore, a =  =  = 6.1 m/s2 to one decimal place.
Using s = ut + ½ at2, u = 0, a = 6.1, s = 4, the required time is gotten by :
4 = 0 + ½(6.1)t2. Therefore t =  = 1.1 sec. |
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