What is the kinetic energy of a falling rock?

[The Futur]

Homework Statement

b) A person standing on the edge of a 100 m high cliff drops a 0.5 kg stone vertically downwards. Determine the final velocity of the stone after falling 100m, and its kinetic energy.

Homework Equations

Final velocity
v = √(2gx)

The Attempt at a Solution

final velocity

v = √(2gx)
v = √(2(0.5x9.8)100)
v= 31.3m/s
is that correct?

how do i calculate the kinetic energy?

 

[kbaumen]

how do i calculate the kinetic energy?

Are you familiar with conservation of energy or the kinetic energy formula?

 

[CEL]

Homework Statement

b) A person standing on the edge of a 100 m high cliff drops a 0.5 kg stone vertically downwards. Determine the final velocity of the stone after falling 100m, and its kinetic energy.

Homework Equations

Final velocity
v = √(2gx)

The Attempt at a Solution

final velocity

v = √(2gx)
v = √(2(0.5x9.8)100)
v= 31.3m/s
is that correct?

how do i calculate the kinetic energy?

The velocity is wrong. You don't use the mass to calculate it (see your formula).
The mass is used to calculate the kinetic energy.

 

[The Futur]

so it will be

v = √(2gx)
v = √(2(9.8)100)
v= 44.27m/s ?

and no i don't know how to calculate the second part

 

[CEL]

so it will be

v = √(2gx)
v = √(2(9.8)100)
v= 44.27m/s ?

and no i don't know how to calculate the second part

Read the page of Wikepedia about kinetic energy
http://en.wikipedia.org/wiki/Kinetic_energy