Question

A bob of a simple pendulum is imparted a velocity 5m/s when it is at its mean position .To what maximum vertical height will it rise on reaching to its extreme position if 60%of its energy is lost in overcoming fricition of air ?

(Take g = 10m/s2).

Answer 1

Initial mechanical energy given to the bob, E = kinetic energy = ½ mv2

At the maximum height say ‘h’ the mechanical energy of the bob is only potential energy, so, PE = mgh

But due to loss of energy in air resistance, only 40% of initial mechanical energy is converted to PE.

So, PE = (40/100)KE

=> mgh = (0.4)(½ m)(52)

=> h = (0.4)(0.5)(25)(1/10) = 0.5 m

Answer 2

⛦Hᴇʀᴇ Is Yoᴜʀ Aɴsᴡᴇʀ⚑
▬▬▬▬▬▬▬▬▬▬▬▬☟

➧ At the maximum height say ‘h’ the mechanical energy of the bob is only potential energy. So,
➾ PE = mgh

➧ But due to loss of energy in air resistance, only 40% of initial mechanical energy is converted to PE.

➾ PE = (40 / 100) K.E

➾ mgh = (0.4) (½ m) (5²)

➾ h = (0.4) (0.5) (25) (1 / 10)
➾ 0.5 m ...✔

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Thanks...✊