JAMB Physics 2010 Objective — Question 8

Question 8 of 50 from the Joint Admissions and Matriculation Board (JAMB) Physics 2010 Objective paper, with the correct answer and a full explanation.

A bob of weight 0.1 N hangs from a mass less string of length 50 cm. A variable horizontal force which increases from zero is applied to pull the bob until the string makes an angle of 60 with the vertical. The work done is

A. 0.250 J
B. 0.025 JCorrect
C. 0.050 J
D. 0.500 J

Explanation

The workdone equals the potential energy of the bob at the new position: P.E = mgh, where h = l(1-cos60) = 0.5(1-0.5) = 0.25m... following the original worked solution, L = 50cm = 0.5m, h = l(1-cos60), P.E = mgh = 0.1x0.5x(1-0.5) = 0.025J.

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