Class 9th Science - Work and Energy Case Study Questions and Answers 2022 - 2023
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Work and Energy Case Study Questions With Answer Key
9th Standard CBSE
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Reg.No. :
Science
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The following diagram shows that a simple pendulum consisting of a bob of mass 100 gm. Initially the bob of the pendulum is at rest at ‘O'. It is then displaced to one side at A. The height of 'A' above ‘O' is 5 cm. (Take g = 10 m/s2)
(i) What is the value of potential energy of bob at 'A' and where does it come from ?(a) 0.05 J (b) 0.5 J (c) 0.0005 J (d) 50 J (ii) What is the value of total energy of the bob at position A ?
(a) 1 J (b) 0.05 J (c) 5 J (d) 50 J (iii) What is the value of kinetic energy of the bob at mean position 'O' ?
(a) 10 J (b) 5 J (c) 0.05 J (d) 50.0 J (iv) What is the value of kinetic energy and potential energy of the bob at the position 'P' whose height above 'O' is 2 cm ?
(a) P.E. = 0.2 J and K.E. = 0.3 J (b) P.E. = 2.0 J and K.E. = 3.0 J (c) P.E. = 0.002 J and K.E. = 0.003 J (d) P.E. = 0.02 J and K.E. = 0.03 J (v) What is kinetic energy?
(a) Energy acquired due to motion
(b) Energy acquired due to rest
(c) Sum of Potential and mechanical energy
(d) It is the energy stored inside a body.
Case Study
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Answers
Work and Energy Case Study Questions With Answer Key Answer Keys
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(i) (a) 0.05 J
The work done in raising the bob through a height of 5 cm (against the gravitational attraction) gets stored in the bob in the form of its potential energy.
PE = mgh
= 0.1 x 10 x 5 x 10-2
= 0.05 J
(ii) (b) 0.05 J
At position A, PE = 0.05 J, KE = 0
So, Total energy = 0.05 J
(iii) (c) 0.05 J
At mean position, potential energy is zero, hence KE at O = 0.05 J
(iv) (d) P.E. = 0.02 J and K.E. = 0.03 J
PE at P = mgh
= 0.1 x 10 x 2 x 10-2
= 0.02 J
K.E = Total energy – PE
= 0.05 – 0.02
= 0.03 J
(v) (a) Energy acquired due to motion
