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 Form 4 Physics Uniform Circular Motion Questions and Answers

A child of mass 20kg sits on a swing of length 4m and swings through a vertical height of 0.9 m as shown in the figure 2.
i).Speed of the child when passing through the lowest point.
ii).Force exerted on the child by the seat of the swing when passing through the lowest. (KCSE 2003 paper 2 question 2(b)).

 (3m 28s)
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Answer Text:
i).Potential energy lost = kinetic energy gained.
#Mgh =1/2 mv^2#
2 x 10 x 0.9 = #v^2#
#V =sqrt 18# = 4.24 m/s.
ii).Force is centripetal = #(m times v times v)/r = (20 times 4.24 times 4.24)/4 = 89.9N.#