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07/01/2022 1:50 pm
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The boxes of masses 2 kg and 8 kg are connected by a massless string passing over smooth pulleys. Calculate the time taken by box of mass 8 kg to strike the ground starting from rest. (use g = 10 m/s2)
(1) 0.34 s
(2) 0.2 s
(3) 0.25 s
(4) 0.4 s
1 Answer
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07/01/2022 1:57 pm
Correct answer: (4) 0.4 s
Explanation:
(m1g – 2T) = m1a – (1)
T – m2g = m2(2a)
2T – 2m2g = 4m2a – (2)
m1g – 2m2g = (m1 + 4m2) a
a = \(\frac{(8-4)g}{(8+8)}\) = \(\frac{4}{16}g\) = \(\frac{g}{4}\)
a = \(\frac{10}{4}m/s^2\)
S = \(\frac{1}{2}at^2\)
= \(\frac{0.2 \times 2 \times 4}{10} = t^2\)
t = 0.4 sec