What is the speed of the bob at the position ...

ICSE Class 10 Physics 2020 Paper

SECTION - II

The figure below shows a simple pendulum of mass $200\ \mathrm{g}$ . It is displaced from the mean position A to the extreme position B. The potential energy at the position $A$ is zero. At the position $B$ the pendulum bob is raised by $5\ \mathrm{m}$ .

Question : 29 of 67

Marks: +1, -0

What is the speed of the bob at the position

A

when released from

B

(Take

g = 10\ \mathrm{m}\,\mathrm{s}^{-2}

and there is no loss of energy.)

Solution:

Let the speed of the bob at position

A

be '

v

Total mechanical energy at A

=

Total mechanical energy at

B

\frac{1}{2} m v^2 + 0 = 10

\frac{1}{2} \times \frac{200}{1000} \times v^2 = 10

v^2 = \frac{2000 \times 10}{200}

v^2 = 100,\ \because v = \sqrt{100} = 10\ \mathrm{m}/\mathrm{s}

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