Reading Fig. 7.39, total energy is 30 J. At P, potential energy is 20 J giving velocity 6.32 m s-1. At Q, potential energy is 30 J giving velocity 0 m s-1. Point R cannot be reached since it requires ...
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For rotational balance, effort times effort arm equals load times load arm. Since the adult has twice the weight of the child, the child must sit at twice the distance from the fulcrum compared to the adult.
Lifting to the 20th floor requires twice the energy because the vertical height is doubled. However, since the time taken is also doubled, the power required remains exactly the same as before.
Statements (iii) and (iv) are correct. At the highest peak, vertical velocity momentarily becomes zero making kinetic energy zero, while the entire initial mechanical energy turns into maximum gravitational potential energy at that height.
Chapter 7 “Work, Energy and Simple Machines” explains the concepts of work, energy and power. It describes different forms of energy and simple machines, helping me understand how machines make work easier in daily life.