(A) According to the law of conservation of mechanical energy,the total mechanical energy remains constant in the absence of non-conservative forces l

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(A) According to the law of conservation of mechanical energy,the total mechanical energy remains constant in the absence of non-conservative forces like friction.Initial mechanical energy at height $h_1 = 100 \ m$ is $E_i = mgh_1 + 0 = 20 \times 10 \times 100 = 20,000 \ J$.Final mechanical energy at height $h_f = 20 \ m$ is $E_f = mgh_f + \frac{1}{2}mv^2 = 20 \times 10 \times 20 + \frac{1}{2} \times 20 \times v^2 = 4,000 + 10v^2$.Equating initial and final energy: $20,000 = 4,000 + 10v^2$.$10v^2 = 16,000$.$v^2 = 1,600$.$v = 40 \ m/s$.

Class 11 Physics Work, Energy, Power and Collision Work Energy Theorem and Conservation of Mechanical Energy

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$A$ ball of mass $20 \ kg$ is at rest on a hill of height $100 \ m$. It starts rolling down,reaches the ground,climbs another hill of height $30 \ m$,and finally rolls down to a horizontal platform at a height of $20 \ m$ from the ground. What will be its velocity at this point? (Assume $g = 10 \ m/s^2$)

A
$40$
B
$20$
C
$10$
D
$10\sqrt{30}$

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Work, Energy, Power and Collision

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Work Energy Theorem and Conservation of Mechanical Energy

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