A stone falling from a cliff ....

Classical Mechanics Level 2

A heavy stone is thrown from a cliff of height h with a speed v. The stone will hit the ground with maximum speed if it is thrown :

(A) vertically downward

(B) vertically upward

(C) horizontally

(D) the speed does not depend on the initial direction.

vertically downward the speed does not depend on the initial direction. horizontally vertically upward

Saumya Shandilya by Saumya Shandilya , 25, India

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3 solutions

Michael Mendrin
Jul 26, 2014

Speed is a scalar, not a vector like velocity. Hence, "maximum speed" is the same as "maximum kinetic energy" at moment of impact. This energy is the sum of gravitational potential plus kinetic energy imparted by throwing the stone. Hence, it doesn't matter which direction it is thrown.

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as v=u+at , so v will be maximum if u will be maximum, so answer should be vertically downwards. please correct me if i am mistaken any where.

Vishal Bharga - 6 years, 8 months ago

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its not true because if u throw it vertically upward , it will reach a certain height and during descending it will gain the same initial velocity at the point of height h and then travels down . So it doesn't matter upon the direction

Yogesh Ghadge - 6 years, 7 months ago
Rohaan Nadeem
Aug 3, 2014

Once it reaches terminal velocity,it doesn't matter what the initial direction was.

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Yogesh Ghadge
Nov 3, 2014

speed is a scalar quantity , it does not depends on its direction

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